Well I'm bored at the moment and wanted to predict the roster for the lols.
I think Sakurai will want to have a lot more newcomers as unlockables. At least I hope so, because the Brawl's unlockables were meh. I think it was only two newcomers, which is just bad. (Not counting Toon Link, since he is basically Young Link, or third party characters we already knew about.) So I think most veterans will be there from the start. Including third parties.
I also think that while Melee and Brawl had 4 characters at most for each series, I think that number will be increased to five in SSB4. So 5 Mario, Side Mario, Zelda, and Pokemon characters.
I will also list reasons as to why I think they will get in.
PS: I may forget some of Brawl's characters because I have bad memory and may not remember everyone that was in it.
PPS: I wll list reasons for some characters and why I think they will get in. This is not my personal wish list, but who I think may get in based on things.
*Means newcomer
Starter Characters:
Mario
Luigi
Peach
Bowser
Link
Zelda
Ganondorf
Pit
Palutena*
Kirby
Meta-Knight
King DeDeDe
Fox
Captain Falcon
Pikmin & Olimar
Donkey Kong
Diddy Kong
Wario
Yoshi
Villager*
Wii Fit Trainer*
Mega Man*
Sonic
Pac-Man*
Little Mac*
Mii*
Marth
Ice Climbers
Mr. Game & Watch
Pikachu
Lucario
Pokemon Trainer
Ness
Samus
Hidden Characters:
Toad* - Got big in NSMBW, NSMBU, and now SM3DW. Of every character he seems the most likely newcomer.
ALBW Link - May be Toon Link or cut due to ALBW being so near the Smash release. But do not think TL is in due to 3DS stage. One of my faves too...
Girahim*(SP?) - He's just bad ass, a huge part of SS, and I hink he'll make it.
Medusa* - Kid Icarus Uprising will get 3 reps just because Sakurai created the game.
Waddle Dee/Other Kirby Character - See above. (Waddle Dee is only notable Kirby character I could think of, may be other character.)
Bayonetta* - Sakurai is friends with Kamiya. Will probably put her in just because of that, maybe keep it hidden since BY is also owned by Sega.
Lucina* - Have'nt played FE:A, but her and Chrom seems likely candidates. Sakurai has said he wanted more female characters so I guess this.
Ridley* - Will be put in based on fan requests, like Villager and Mega Man.
Mewtwo - Will be re added due to them bringing himback into the spotlight. Already been hinted at.
Igglybuff* - Like Pichu, Sakurai will create a weaker clone of Jigglypuff for the lols. Jigglypuff would be cut. Mainly because Sakurai will want a new Pokemon character, but wouldn't do six Pokemon characters without doing six Mario & Zelda characters.
R.O.B.
Lucas
Falco
Dixie Kong*
Pikmin & Alph & Brittany & Charlie* - Pikmin 3 was Miyamoto's main project. His baby. He will want them to be in, even if it will probably be cloneish. :/
8 Bit Mario* - The final unlockable. Smash has always been about paying homage to Nintendo classics. What better way than with a 8 bit Mario, that is literally a flat sprite and in its small form. (And yeah I know this would make six Mario characters, well we could just slot it into a retro row...IDK. Just seems like something that could happen.)
Wolf cut due to it seeming unlikely to still have 3 Star Fox characters when the franchise is dead.
Snake cut because Kojima doesn't put MGS on Nintendo systems.
Ike could go either way, don't know much about FE. Just going by the pattern of replacing the secondary character with a character from the recent game.
32 Veterans + 18 Newcomers = 50 Characters. (I wasn't even aiming for 50, just added this all up as I went alone, heh.)
Now that I finished it...yeah, 18 Newcomers seems really unlikely. Well, I will stick to this however and see how close by predictions get.
And yes, I count Igglybuff as a newcomer but not ALBW Link
Now, here is my wishlist:
Palutena
Medusa
Geno (He is awesome.)
Girahim
A 8 Bit Luigi charcter instead of Mario.
Dixie Kong
Kiddy Kong (Dat DKC3 Nostalgia!)
Female Pokemon Trainer
Female Villager (Please lettuce import NL characters!)
Tetra (Not in a Shiek way.)
Waluigi
Mario & Luigi RPG Tag Team. (GIMME!)
Yoshi & Baby Mario Tag Team (Nostalgia again...)
I'm sure theres more, maybe even my favorite, but can't think of them off the top of my head...