So, if we are to take under consideration all the recent leaks as well as the hints and teases provided, we can disclose the following characters in the game:
Veterans (10): Dr. Mario, Wario, Ganondorf, Falco, Jigglypuff, Mewtwo, Ness, Ice Climbers, R.O.B., and Mr. Game & Watch
Newcomers (9): Bowser Jr., Dixie Kong, Impa, Ridley, Dark Pit, Shulk, Chorus Men, Mach Rider, and Duck Hunt
Cuts (8): Young Link, Wolf, Ivysaur, Squirtle, Pichu, Roy, Lucas, Snake
So...best case scenario, we get the 56 playable characters total including the Mii Fighters (counted as one).
PS: I added the Ice Climbers back onto the roster simply because Ninka's source isn't 100% certain about the cuts; 4Chan 19 was simply spliced together crudely and likely just made the assumptions; and 4Chan 20 and two of the three sets never stipulated that Ice Climbers was indeed cut. The DLC comment was ruled out as being most likely false, though the mods won't go into detail why (it was the very last comment before the thread was locked down). While I am sure that Wolf will be back, he is likely to be of the lowest priority this time around, so he can indeed be gone. If you have to switch one of the newcomers out for Wolf, then go with Mach Rider instead. Poor Richard leak, as far as I can tell, is the only leak overlapping with these that can be called into question.
Edit: Failed to realize this wasn't the leak thread. Whoops! Oh, well. It's about the characters, anyways.