OK, So here's my thoughts on Returning/Wanted characters, and signs on why they MIGHT be in and why the MIGHT NOT be in
Snake:
+ Unique moveset, not many nintendo reps could use all of his moves
+ Was the best moment of the original trailer, made a lot of people surprised and excited to play smash
- MGS GS/TPP Snubbed Nintendo
- David Hayter snubbed as snake
- Should have probably already been revealed
- A lot more voiceover work for codec calls would be required
- Sheik stole his grenade
Ridley:
+ If he's not in, why not just show him outright, and not a silhouette? What's the purpose of the tease?
- Tease might just be to hype that ridley is actually in the game, vs not at all (average fan is supposed to think, wow how cool, ridley is a stage boss!', not 'Oh man, ridley isn't playable')
- He's probably just a 'boss hazard'
Palutena:
+ Removed from pit's final smash
+ Trophy tease RIGHT after showing she was removed from pit's final smash
+ Kid Icarus uprising fleshed her out as a character, gave her a personality and a potential move set
+ Sakurai is responsible for Kid Icarus revival. It's his game, and he can show favor toward it
- Palutena is a statue on a stage. No other smash character is a statue on a stage.
+ Toon link is replaced by alphonso, so being on a stage doesn't mean you can't appear in the game
- She is a goddess!
+ So is rosalina!
Squirtle:
+ Unique moveset
- Greninja
Ivysaur:
+No plant type starters
+Unique moveset
- Too many pokemon reps already?
Mewtwo:
+ Mega evolutions of pokemon X/Y made him popular again
+ Has a fairly unique moveset, excluding his neutral B, which is somewhat similar to lucario
+ No other psychic type pokemon
- Too many pokemon reps already
- Might have officially been 'replaced' by lucario in brawl
Captain Falcon, Ness, Jigglypuff:
+ Been in every smash bros
+ Jiggly has always been secret
+ Ness/Falcon were secret in 64 and brawl
- Luigi has already been revealed, and he was always secret
+ Luigi was probably an exception for 'year of luigi'
Edit:
Pac man:
+ Galaga guys are in the game
+ S-flag in game (from rally-X) [thanks Zonic 505]
+ Namco bandai working on the game
- He's a dumb character for a fighting game, classic version lacks personality entirely
+ Sakurai is a smart guy, and if anyone can make him work, it's sakurai and team
+ He's already raced alongside mario in mario kart arcade games
- A lot of people, myself included, don't want him in. Doesn't mean what we think matters, though
Mii:
+ Huge part of nintendo's history since 2006
+ used in dozens of nintendo games
- Already appears in background of find mii stage
- Could be used for profile purposes (global smash power, online avatar), and not actual fighting.