Seeing as how I fudged up on the past attempt and want to make sure it gets properly read this time, here's my reposted predictions:
Original 12 *Mario *Luigi *Link *Donkey Kong *Samus *Yoshi *Kirby *Fox *Pikachu *Jigglypuff *Ness *Captain Falcon
Likely Returning Characters (besides Original 12) *Peach *Bowser *Zelda/Shiek *Ganondorf *Meta Knight *King Dedede *Wario *Diddy Kong *Falco OR Wolf (but not both) *Pit *Marth *Olimar *Ice Climbers *Mr. Game & Watch
Likely New Characters *Palutena *A new Pokemon (humanoid in stature) *A new FE character from Awakening *At least two new NES-era characters *Two third-party guests (at most)
This is not a full roster, but just me predicting the ones most likely to get chosen for it. And PLEASE don't say anything about Shulk because I have no reasonable opinion for or against the character (I'm going by what I recognize).