Wow, loved to read this. Although somethings I have already figured it out, I'm still going to comment, because I like to.
Yes, Yama-ji is already a goner I think. From what I understand, and what he said, Juha is the only that can take Yama's bankai, meaning that his strength is as great or ever greater than Yama's, I wouldn't admire myself.
I think Byakuya will die somehow but I don't think Toushiro will, Kenpachi will not die for sure, because of his relationship with Yachiru, meaning that she will save him at some point, it's very likely this will happen, I really don't know.
About the medallions, Kisuke will, eventually, find a way to counter attack those medallios, because he's so damn good.
About Aizen. The way the Arrancar arc ended, I think they shouldn't put Aizen back, atleast not him being present if that makes sense, what I'm trying to say is, if he shows up in flashbacks or that, I don't mind, but if he somehow starts interacting again in the story I think it will be bad, but I don't know since you mentioned that Aizen said "That Thing", and that whole Spirit King being a human could be possible.
About Uryu, he will have to show up eventually, so I agree with everything you said about it.
And I didn't know that Kobu said all bankais that haven't been shown are going to appear, so I'm hoping Yoruichi's will appear too.
I agree with you in everything there I think, so yeah. The only thing that I don't see happening is they(Ichigo etc) invading the Vandenreich base, I don't think it makes much sense, I don't know, atleast if they do that, I don't think it's Ichigo, but the arrancar, like Nel and so on, but that remains to be seen.