The main villians that are coming back are pretty obvious. (no i dont mean maleficent/pete.) Braig and Isa I can see making an appearence in the game, but I think at the very end it will show the newly incarnate Xehanort. As for the shocking ending, maybe that is it right there. I can't really see Riku/Sora falling to darkness. I do think it would be shocking to see Sora fail the exam, then turn to xehanort's side. But I dont think that will happen. I cant think of anything more shocking, so I hope Nomura pulls this off well, and doesnt give up another e3 disappointment.