I think we are extremely likely to see Wario, Meta Knight, Captain Falcon, Ness, and Ice Climbers sometime before release. Falco is a pretty strong possibility too but could maybe be secret, and while Ganondorf and Mr. Game & Watch are shoe-ins to return, I feel both are likely secret. Pokemon are very hard to predict and we probably will have at least one if not both of Mewtwo and Jigglypuff in the game, but any more Pokemon have a strong possibility of being secret (Jigglypuff being the first and easiest character to unlock like in 64 and Melee would be a very "Sakurai" thing to do). Ike, Lucas, and Wolf are all among the most likely cuts at this point though any that do return are likely to be shown soon, and R.O.B. is both among plausible cuts and very likely to remain secret if he does return so it's quite likely we won't be seeing him anytime soon. I consider Snake already confirmed to be cut based on Kojima's comments, but some disagree on that. I think that covers everyone of note, and that will keep up a steady stream of veterans until release with probably any remaining starting newcomers shown at or around E3.