Board Thread:General Discussion/@comment-27140233-20151102183905/@comment-26091912-20151103082318

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 Bankai 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.