Throwing in my 2 rings into the topic, but here's my prediction:
Veterans:
Rest of the original 12 (Jigglypuff, C. Falcon and Ness, although all 3 could be revealed before the 3DS version comes out)
Ganondorf (with completely redone moveset)
Wario/Meta Knight/Falco (if both aren't in the May reveals (which has a 50/50% chance of happening), then they'll get revealed here, or could be revealed in the same manner as the 3 above characters, Falco isn't going anywhere and is likely to get revealed either during E3 or possibly end up as the July reveal (assuming the 3DS version is out around late August/early September)
Mewtwo (Pokémon had 6 reps before and it's bound to happen again, plus it would be stupid on Sakurai's and Pokémon Company's parts to not include him back in the roster, since he had a lot of hype going into Gen VI and had a movie, if he's left out once again, then Gen VI and M16 would have generated all that hype for nothing)
Mr. Game & Watch (probably might be revealed after E3 is done, or could end up in a similar case as the 3 remaining Original 12 characters and Wario/Meta Knight)
Ice Climbers (if the 3DS version is still suffering the issue of having multiple 2-in-1 characters sharing the same screen together (although this may have been resolved thanks to Rosalina's inclusion), then they could be separated and go the same route that Sheik and Zero Suit Samus took to stay in the roster (although their cases were due to the transformation mechanic in Melee/Brawl), by making Popo and Nana their own character, with different movesets for each of them)
Newcomers:
Chrom (hate to say it but Ike's all but cut at this point. EDIT: Ike's back, so this gives Chrom a 50/50%)
Palutena (she's basically in either way, those leaks are very hard to ignore)
Pac-man (he's all but guaranteed now, since we have 2 of Namco's Big 4 classic arcade games represented (being Galaga and Rally-X), he's likely going to end up being the main event for the entire Smash Bros presentation just as Megaman was last year)
Shulk (he's highly wanted both in Japan and America, so why not)