I'm glad they made the cuts they did in Brawl. Doctor Mario, Young Link and Pichu (and KINDA Roy) were really just waste of space. Doc was 99% Mario, with some power and speed changes. Young Link the same, though he had Fire Arrows. Pichu too, except for wall jumping and self-damaging. Instead of making them, they could instead make 3 other completely unique characters, like Wario instead of Doc, Charizard instead of Pichu, Skull Kid instead of Young Link. Luckily, the clones we got in Brawl wasn't that much of clones anymore, and the cut the big clones from Melee (Mewtwo though... he should still be there D'
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Anyway, Sakurai said "no more clones" for the Smash 4, but yet we got Toon Link. I know he can play very differently from Link, but come on! His special moves are all the same, just a little different! Why not give him, let's say, Bomb-Chus, Deku Leaf, Skull Hammer, etc?
So, if Toon Link returns, I think there is a chance of Lucas returning as well, but I believe the chance is small. As people here have mentioned, the game Lucas was in was a Japan exclusive, but Toon Link have got a recent game (Wind Waker HD).
As for other vets, Jiggly will return. She is one of the original 12, so even though I don't like her personally, it would be sad to have one of the original smashers gone. Since Jiggly now is a fairy-type Pokemon, they could give her another moveset; get rid of her Slam side-special and give her something like Gazzling Beam (I THINK it's called that. A new fairy-type move). And buff her Up Special. It was nearly useless before. Doing that will make Jiggly 10x more interesting in my eyes.
Ness comes back. As I said, the original 12 will return. Same with our Captain Falcon.
Wario. He's back, no doubt. If Rosalina gets in from the Mario series, Wario will too. Besides, Waluigi and Ashley had a W mark instead of a mushroom mark. And please, PLEASE make his animations the way Wario really is. In Brawl, he has Mr Game and Watch styled movements. I know it is from Wario Ware, but that isn't how Wario is!!
Give him movements like he has in Wario Land, Wario World, and the Mario Party/sports games!
Ice Climbers. This is where I get doubtful. Sakurai said he had problems developing them on the 3DS, so who knows? Maybe Rosalina has taken their place?
Mr Game and Watch, I see him returning as well, being a fan-favorite (even though I don't care much about him, lol)
Falco, I think he will return, getting a new moveset, making him more different from Fox. As for Wolf, I do think he will be cut.