Ridley discussion should go in his thread in the Character section, people. This thread's just for discussing reveals, not the characters themselves.
Anyway, I'll make my list. It's set up so that the most likely are at the top, and then they dwindle down.
Veterans (Assuming they're not shown prior to E3):
Wario
Ice Climbers
Ness
Meta Knight
Mewtwo
Ganondorf
Ike
Newcomers:
Palutena
Mii
King K. Rool
Chrom
Shulk
I purposely left out Third Parties. I think if Pac-Man and/or Snake are in the game, it's E3 or bust. Considering the 3DS version hits stores this Summer, E3 is the only time to market them, which they would need to do prior to release. If they're not shown, they're not in. Simple as that.
Also Ridley. I don't have hope for him anymore, but if by some miracle he were playable, it'd also be "E3 or bust."