i will tell you who
imo,it would be a bit bad if uryu became an enemy out of the blue,now. it's too late to have him as an enemy,and most of the mangas/films have got a friend who becomes an enemy,so it won't surprise much.
I hope no one gets kidnapped this time. The entire Orihime angle that got thrown out just pissed me off to no end.
It's true that for the final arc of Bleach, it would make the most sense if it's not a "rescue a nakama" arc, but "save the world and aaall the nakama" arc. We can expect quite an Ishida centered arc (but that doesn't mean he'll really be the center of the plot... see Arrancar arc) since Kubo himself said that every arc is about one nakama and this one will be Ishida's (doesn't mean he'll be kidnapped though).
Well, it's all about Quincies, so Ishida is a strong name right now.
I can see Ishida joining the Vandenreich, at first.
But then, he'll see the begining of the break in balance and i think he's going to be against Vandenreich when that happened. That's when i imagine him being made prisioner.
Just a possibility.
Matsumoto Rangiku , she is too hot to be killed , so the quincy mohawk guy kidnaps her and hitsuguya , renji and hisagi get fanboy rage and go bankai and we see their improved bankais and hisagi achieves it upon hearing matsumoto scream 'save meeeeeee'
kira would be there too if he didnt have half his body vaporized
I would say Karin or Yuzo or maybe both. I think that Ichigo, Isshin, and maybe Rukia would go help and rescue them. Rukia may get a few more soul reapers to come or their friends back in the human world something like that