Hey, hey. This is where suggestions for Smash 5 are posted, right? Well it is now. Here's what I've got.
New characters--
Prince of Sablé
Phosphora
Saki
Skull Kid
Takamaru
Waluigi
Bring back Ice Climbers and Mewtwo (but make Mewtwo different enough from what Lucario is now)
Mr. Resetti would be cool to have as an assist trophy again, too.
And that's what I've got. 'But guavadorf!' you might be saying, 'Those new characters are all assist trophies now!' Fair enough. But seeing them in play made me realize that they would probably make good full-fledged characters. Some of them seem to be better personalities and more unique and representative of their series than... well, I'm cool with the current roster. It just seems like those six (plus one if you read the second to last paragraph) seem to have both a better future and history with Nintendo than people like Shulk or Robin (or Pac-Man, even). And I know moves could be made with them, because a) some already have, and b) moves can be made with anyone.
Not to sound like I'm complaining. I dig the 3DS Smash, most definitely. I'm thinking way too far in advance, possibly.
Oh yeah, and the Flying Man, too. For the lulz. If he wasn't famous before, he is now.
Since I accurately predicted Robin and Lucina getting in the game with no Chrom, I'll say that at least four out of those seven will make it into the next game, for a safe bet, when and if a next game exists. We'll see.