I don't think they'll bring back Young Link or Pichu; Dr. Mario maybe as an alt. costume if Sakurai is allowed to use alt. costumes, which he said couldn't be done because the official Nintendo character model had to be used alone. Mewtwo has a fair chance, but is no shoe-in. Roy has fanboys here and there, but I doubt he'll return over Ike.
Wolf and Lucas are good except for Final Smash, Falco can use more differentiation, and Luigi needs the Poltergust as a Down Special, and I wouldn't mind seeing his fireball being turned into green electricity. Toon Link needs some more unique Specials, and Ganon...good lord, give him a sword-using set, and one that makes him higher on the tier list. If Sakurai wants to please old Ganon users, give us Black Shadow as a clone from the same series and with less unique potential.
I hope Sakurai will learn from his mistakes. It seems like he spent the most time on the SSE, and as he put it, "Distilling gameplay", AKA casualizing the game. I think a roster of 50 is our best bet, maybe 51, as a throwback to the 1 extra that Smash has used before (51 and 41 event matches in Melee and Brawl respectively).