I can't see any more new characters revealed at E3, but we probably still have 2 more Pre-ballot "Mario"s.
1 is
probably Wolf.
The other will be someone who was planned but cut for time constraints. Maybe a newcomer. Like Isaac. Or Dixie. Or K. Rool. Or a Rhythm Heaven rep. Or maybe
,
, or
Either way I doubt we'll hear about them at E3, Nintendo want us to look at Roy and Ryu (and Lucas) for now. At best they'll give us a notification that Wolf is on the way (like Mewtwo's announcement), then give us game-play of him, and whoever else, in a later direct. They would release around October, by which point Sakurai would have moved onto the ballot characters.
The wait continues...