I agree with Ethnic Woman about Braig, especially the bit about mortally wounding Xehanort in the process.
As far as who I expect to die: Eraqus (if not already), Braig, Xehanort, and AtW.
As far as who I want to die:
If Eraqus comes back, he should die for real. I want someone in RAX to die if they come back. I sort of want Riku to die, too. I feel like since he's been through so much and he's just turning his life around and learning how to balance darkness and light, his death would be that much more tragic. Then he'd give a monologue about how he could die in peace knowing that he'd set things right with himself and everyone, and it would be really sad but sort of happy.
Actually, that's really cliché. Still sad, though.
I want Aqua to die, and yet I don't. She's one of my favorite characters, but that's also why I want her to die. I guess I just want something unfathomably horrible (sadistic, much?) to go down, and Aqua's the best candidate. I mean, she reunites with Terra and Ven after twelve years, and then Xehanort just stabs her or something like that. Not like I'd expect it to happen, but still.
As long as KHIII makes me cry like the little girl that I am, I'm all set. If not, I will be very disappointed.