Some issues. Your 1st theory misses some points. Zanka no Taichi corresponds to the four cardinal directions (North, South, East and West) They are not stages, 2 are active from the onset and the other two are only used if necessary. The use of the bankai is so powerful that it can consume everything if used too long. Katen Kyokotsu: Karamatsu Shinji seems to correspond to a play with each act being more devastating in purpose then the last. Shirafude Ichimonji sole purpose is to act in conjunction with its shikai ability to name or rename. What they in fact have in common is they are the bankai of some the greatest shinigami around. Seeing as a zanpakuto is reflection of its wielders power.
Your 2nd Theory is flawed on the account that your using the rational of someone neither a shinigami nor does he have a zanpakuto to make a determination on how such a thing works. you say "When a Shinigami achieves the true power of his Bankai, with its full name, the Shinigami enters a similar state as his zanpakuto spirit fusing with his zanpakuto." You really dont have any proof to go on with this assertion. What is a "true" bankai? whats to assume that a bankai doesnt have its full name from the onset (it only happened once with renji and it wasnt a issue of a full name but the correct name), and the last part is not really accurate.
Yamamoto was surrounded by the heat of his bankai from activation, he only made it visible by willing the flames to be seen to demonstrate what was protecting him the entire time.
Shunsui's zanpakuto spirit being present doesnt confirm anything that can be true of anyones zanpakuto spirit for all we know, its being brought out which is the purpose of bankai.
Komamura's bankai exists in a symbiotic link with him, thats the nature of how it works.
Aizen is more or less confirmed of having lost his zanpakuto not fused with it. Seeing as he believed himself beyond the need for it. We dont know what happened with yhwach but it was minor.
Rukia taking a new look in bankai is not unheard of for a bankai, we cant determine what her zanpakuto spirit looks like until we see it in the manga.
Mugetsu is a technique of the Final Getsuga Tensho, its an attack not a form so how can it look like yhwach with the shadow of multiple eyes over his face. Also ichigo was wrapped up in bandages with long black hair.
Renji is the only instance that if given a incorrect name like with a shikai your gonna get a different look and/or powered bankai.
Most importantly none of this fits to your theory. The argument could be made that a bankai would have to be used with its correct name for its power to be fully used but thats about it. Also the very concept of bankai is bringing ones zanpakuto spirit into the physical world. Just using a bankai in general achieves that without a specific zanpakuto form being required to manifest.
As for the conclusions they are somewhat confusing and misleading. Byakuya's zanpakuto didnt change so why would he had a new bankai. He himself said he retrained with his shikai to realize the great power it had for himself not that it was new. In turn his bankai would still be the same. Also Ichigo's shikai has changed to acknowledge his quincy and shinigami halfs using a long and short sword whatever his bankai will be it wont likely give any preference to anything more then his shikai does as a shikai is a zanpakuto's true form.
^ I think what he's trying to convey is that when a Shinigami has fully mastered their Bankai, they take on an appearance resembling their Zanpakuto spirit. And their Bankai also becomes more physically fused with their body.
Renji is also the first one to reveal his Bankai after training in the Royal Realm. So it is possible that Byakuya and Ichigo could have a "new" one, as well.
Besides, it's not like Ichigo's Bankai hasn't changed appearance before.
Except there is no proof of that as i pointed out. Yamamoto took on no appearance its part of his zanpakuto's techniques. Actually in the entire series outside of Rukia, Hitsugaya, Renji, Ichigo nobody has been seen wearing their bankai. Also Renji was wearing his previously before the arc. Its also not from training in the royal realm its even explained his zanpakuto spirit didnt have faith in Renji and told him a incorrect name so Ichibe just gave him the correct one. It has nothing to do with fully mastering which comes after years of training which has not happened for either rukia, renji or ichigo. Hitsugaya's hasn't changed and he has had years of training. That was my point. Also at what point does a bankai become fused with ones body, thats said nowhere in the series. Zanpakuto spirits are just a shingiami powers given form hence why they have similar reiatsu and personality as their wielder. Also Its not possible for Byakuya to have a new bankai nothing was wrong with his zanpakuto for to be different, in fact his bankai was stolen and he didnt get it back to after he returned. Also bankai's just dont randomly change. Renji and Ichigo both had broken bankai's their zanpakuto's needed to be reforged. Ichigo wasnt even using a real zanpakuto and and renji was using the wrong name. Hence why they walked out with different stuff.
Yamamoto could be the exception—not the rule. But in any case, his Reiatsu takes the form of flames which covers his body.
In fact, apart from Gin and Byakuya, everyone else's Bankai either manifests in the form of a creature/being, or they "wear" it.
Sui-Feng's is a missle launch pad attached to her right arm, Kensei's is brass knuckle blades with bands on his arms, Komamura's takes the form of a giant samurai which is deeply linked with him, Ichigo wears a black robe which is part of his Bankai, etc.
As for Hitsugaya's Bankai; well, it actually has changed. In addition to ice hands, feet, tail, etc. He now sports ice horns on his head. And we see that his Zanpakuto spirit takes the form of a large dragon. But he's always worn his, so he's irrelevant.
Also, no one said Bankais change randomly, they change depending on the wielder's mental/physical state. Komamura removed his heart which made him "immortal", therefore, his Bankai was immune from harm. Ichigo learned the Final Getsugo Tensho, and his blade became attached to his arm. When his powers returned, his Bankai changed appearance again, due to the traces of his Fullbring powers.
Anyway, we'll find out soon enough whether or not he has a new one.
Also when Hitsugaya's Bankai return to him, the dragon was fuse with him. (When he got infected with hollow powers.)
Let's wait for now and see. I still think this is possible since Yhwach said that Yamamoto's Bankai change from 1,000 and Bankai's don't change randomly like you say. Kubo said that Ichibei and Yamamoto have a connection, i doubt is blood related. I'm aiming for my theory of Ichibei telling Yamamoto the full name of his zanpakuto after the war.
Also, about theory 1. I was referring that both Yamamoto's and Kyoraku's bankai have four abilities or stages whatever you want to call them.
Yamamoto> North, South, East, West= That's 4
Kyoraku> Dan 1, Dan 2, Dan 3, Final Dan= That's also 4.
Let's wait and see. But i still bet that Byakuya's new Bankai is gonna look like his zanpakuto, with the armor.
Your basically trying to pick at random here. The point is the theories arent supported and in order to support them you overlook certain points of fact to fit your argument. Yamamoto is allowing one to see flames, the flames dont really exist. "Could be" doesnt mean "is" which is my point, this is a fact that is stated in the series. Also your advancing the concept of "wear". In this instance we mean actual form change of something over the clothes or new clothes. Not a weapon which is simply what Jakuho Raikoben is as well as Tekken Tachikaze. Komamura's bankai takes the the form of a giant samurai but he isn't wearing it, also it being linked to him doesnt change the fact that he isnt wearing it but controlling it.
As i stated before Ichigo, Rukia, Renji and maybe Hitsugaya (whose form changed temporarily because its ice, which is easy to change, but more importantly because of the hollow influence at the time he got it back). Also to make the point that a bankai changes based on a wielders mental/physical state isnt a universal concept. Komamura had a special technique that isnt inherent to a shinigami but to one that comes from his specific tribe. He is the only one of his tribe to become a shinigami and he has a specific kind of bankai. In turn he has a one time technique that corresponds to his bankai that is unique to him due to how it works because of the unique technique he used to change himself. Huge exception, very unique still not something one can say he wears, that argument is about connection but more importantly only affects him. Ichigo you cant even use as a argument due to the rampant inconsistency and the fact of him not being a normal shinigami, if he was then you might have something. Both are special circumstances that arent reflective of a typical shingiami situation. Also once again the FGT is a technique of his bankai and not his bankai itself.
Didn't Ichibei said that Ichigo became a true shinigami? Meaning that he could have lost his quincy and hollow powers. We still don't know that. But when Byakuya activates his new bankai with the armor, you will see my point.
Let me resume it: When a shinigami achives his true bankai, the user takes somehow the form of his zanpakuto form or powers, like its been said over the years the zanpakuto and the shinigami are one and the same.
Edit: Yamamoto's Bankai power is flames that are condense into the edge of the blade. Second stages activates also automatically, which means he is wearing it even if the opponent can't see it, is still there. Fake Yhwach's sword got destroy after touching Yamamoto's invicible flames.
I agree with that your argument is flawed. 1) You are saying that a true bankai changes the user appearance, which would say that a shingiami who’s appearance did not change most not be using their true bankai? That would mean Gin, Mayuri, Rose, Tosen and Retsu have not been using their true bankai’s which is ridiculous, as we still do not know what is and what is not a true bankai 2) You talk as if you know for a fact (which you don’t) that Byakuya’s bankai will now have armor, but what would you say if he doesn’t have any armor that he’ still not use his true bankai? 3) As for the whole Ichigo thing, Ichibe and Tenjiro where talking about how Ichigo has now become strong like a true shingiami. Nowhere did he say Ichigo lost is other powers and now is only a shingiami.
You are talking like it's a fact when you say something like But when Byakuya activates his new bankai with the armor, you will see my point. Also if he did have armor that still wouldn't change anything as Gin, Mayuri, Rose, Tosen and Retsu still did not take a new from.
A theory needs to be substantiated, meaning there has to be some evidence or justification to base your idea on. You would also have to explain why your theory is legitimate. Lastly for any of this to be a theory it has to have predictions that can be confirmed so that in the even that it isnt confirmable it can be rejected as it cant be supported by facts. So far you have said there is a "True Bankai" (whatever that is supposed to mean cause no real reason is given for what your saying) based on your own criteria having nothing to do with whats established in the series information. You are actually stating things as facts with no way of explaining how they can possibly considered as such. Lastly I don't think most people would put themselves in a position of determining what they say if something was true based entirely on limited information.
Rukia not having a bankai previously is true of anyone who hasnt had a bankai reveled we just dont know what it looks like. Not sure why you bring that up.
Renji's bankai named changed. the reason was precisely given for what the situation was there.
It states a bankai evolves over time with the strength of its wielder thats a fact of the series.
You just stated something "Ichigo's New Bankai will definetly not have the same name Tenza Zangetsu." and "Byakuya's Bankai and name will also change." once again stating something as fact. these two things are opinions, unconfirmed and unsupported opinions that you possibly cannot know. You should not list such a thing anywhere cause its misleading to others and shows a complete disregard to the fact that you dont write the story. This can not be considered speculation its basically fan fiction.
Also your intentionally going out if your way to state something fundamentally false at the end. Where anywhere does Ichibei have the power to prevent Shinigami from achirving their true bankai' form full power. Thats not remotely true on any level.
Gin, Mayuri, Rose, Tosen and Retsu are all dead, except Mayuri but we now he didn't achieve Bankai like the others, he created and modify his zanpakuto and even if the others were alive the concept was introduce in this arc. Or maybe is only given to does who train in the Royal Realm, Ichibei could have taken Yamamoto to the Royal Realm and teach him the full name of his zanpakuto.
I assume this because fake Yhwach said that Yamamoto's Bankai change from 1,000 years ago will saying what you said that Bankai's don't change randomly. Yamamoto had the same problem as Renji.
Why is it that the Zero Squad and Yamamoto's zanpakutos are not in a form of a normal sword before release? Yamamoto's zanpakutos was a wooden stick before release. But this contradicts Renji, Rukia and Ichigo's new zanpakutos looks, so it doesn't count. I'm not saying that you are wrong either, i'm just speculating what would happen if this was true?
It does not matter that Gin, Rose, Tosen and Retsu dead they still did change when they used bankai.Which is what you are saying is a true bankai, Yamamoto's bankai most likely changed because he had 1000 years to master it. Also Ichibe and Tenjiro are the only Royal Guard members to have their swords in a different from.
This is all about a situation that specifically happened to Renji that has nothing to do with him training in the Soul King Palace other then he was finally somewhere were someone in the know reveled a truth about his zanpakuto to him that his zanpakuto was keeping from him. This is not the same for anyone else its Renji specific. You cant deduce from one instance that its true for everyone. You would have to believe a whole set of events that arent supported. Not to mention he didnt have a new bankai based on anything other then he was using the wrong name thus totally changing the configuration of elements of his bankai that already existed in his previous bankai with the incorrect name.
Also once again your making a determination based on the views of someone not a shingiami who does not have a zanpakuto. Bankai's evolve with the strength of their wielder this is established and referenced fact from the series. You are equating with what happened with Renji to Yamamoto based on no evidence. His Bankai blade technique once having fire and later after many years evolved to internalize fire in the blade. There is no proof of a name change or anything except that in 1000 yrs since the technique was further perfected.
Its like you purposely disregarded what this wiki is for cause if you had you could have read referenced facts all on this page about everything known about zanpakuto http://bleach.wikia.com/wiki/Zanpakuto instead of making your own conclusions based on a incomplete understanding of the material.
Also what does Yamamoto and Ichibe having different swords have to do with Ichigo, renji and Rukia? Now you say that you are speculating instead of presenting a theory which is two different things proving that your just pulling stuff out of thin air.
A Bankai either fuses to/surrounds the wielders' body, or it takes the form of some being which resembles (or in the case of Kyoraku, is) their Zanpakuto spirit which they are linked with. The exception being Gin and Byakuya. There's no contesting that. And Bankais have changed appearance on more than one occasion, for whatever reason.
Yes, these theories are flawed, and yes, this is just speculation, but the conclusions are still entirely plausible. There's no need to nitpick over something so trivial.
Nobody is nitpicking of trivialities. This guy is using incorrect information and stating opinions as facts. Thats inherently wrong on any level. Secondly if its not referenced content your making it up. Fusing (to join or blend to form a single entity) That is not what happens. When you state stuff like that it sounds like you dont know what your talking about. They are releasing their zanpakuto's final form to manifest their zanpakuto spirit into the physical world. A bankai can be something worn or a large version of the shikai ability or creature. It is not something you decide is gonna happen with no proof, which is whats constantly being stated here. The only bankai's that have changed appearance are Ichigo's and Renji's (possibly hitsugayas).
Ichigo can see his zanpakuto spirit, so can renji, hitsugaya and Shunsui. That has nothing to do with their bankai, you can make the argument that all shinigami can see their zanpakuto spirit. It would make sense they have to communicate it on a deep level. Still that has nothing to do with this post.
You cannot have flawed theories, baseless speculation and think you have a conclusion.