7. Obi-Wan Returns
There's already some suggestion that Ewan McGregor will return for Rogue One, but what if he's going to reappear earlier in the timeline, realising that long gestating promise made to his former apprentice? Having the Master return would be as equally a fan-baiting moment as if Darth Vader was to rise again, and it would fit with Hamill's promise of a jaw-dropping twist. It's more likely, however, that a return for the character would be the means of transmitting that twist, rather than being the twist itself.
Any Evidence? Only if you're still confused about Obi-Wan's final threat to Darth Vader. Just before he eats lightsaber, Kenobi offers the ominous suggestion that he will "become more powerful than you can possibly imagine" if he's cut down, and though he becomes one with the Force, is that really true? As a Force spirit, all Obi-Wan does is whisper in Luke's ear (he's not even the key Jedi in his evolution), and there does appear to be some disconnect between the threat Could LucasFilm have been playing the longest of long games?