Well holy fuck.
So, yes, everyone was right - it was a "Juha Bach" clone who went down, leaving the "real" Juha Bach to suck up Yamamoto's bankai - and, presumably, decimate him. I do think this is Yama-jii's last stand. Sad, right? I used to hate Yama-jii for how rigid and unyielding he was, but the way he came around to accept Ichigo and the way he tried to protect his shinigami warmed me up a lot. Not to mention that, without him, the shinigami are up a creek. Because from the looks of that final panel, this may be the end for him.
But that was not even what surprised me the most this chapter. Kubo keeps taking the story in directions I do not expect, because I don't think I could've anticipated that Aizen, of all people, would be the special war potential they're trying to reach. I do think it's interesting that Juha Bach says that, initially, Aizen refused their offer; that seems very in-character with what I know of Aizen, who wouldn't want to lower himself to consorting with just anyone. Juha Bach seems fine with that and believes he'll have an eternity to persuade Aizen to see things his way.
And I....wonder.
I can't imagine Aizen serving under anyone, though I suppose I can easily imagine him slaughtering Juha and taking his army. I wonder if Aizen has the same interest in Ichigo as before and if Ichigo's long-ago sympathy for and understanding of Aizen when he was defeated - remember that? - will play into this. I've often wondered if they might not end up as accidental allies. And one does wonder how the remaining Espada will feel about this. Aizen's presence would blow everything right open, no? Remember, back during their final meeting Aizen screamed at Urahara that at least part of his motivations tied back to the spirit king, so I have a funny feeling we might revisit that in one way or another, as well.
I wonder if Unohana will step out to fight with Yama-jii down?