You think every character will be revealed before launch? I don't understand that. Having no surprises in the game would leave many disappointed. It would be okay if we knew they were going to reveal everything, but we don't know that, so once we do know everything, it would be reasonable to assume there is more on the game itself. If there isn't, people will be disappointed.
Why would they set themselves up for disappoint like that? We had 4 nonveterans we weren't told about ahead of time (excluding leaks) with Brawl (Toon Link, Lucario, ROB, and Wolf). I think four is a good number, and it seems Sakurai thinks so to. I suspect we will have a similar amount of unknown newcommers this time around. And that's assuming only the true surprises aren't spoiled. There may well be some vets we don't hear about beforehand as well.
Also Sakurai's pace could easily change.
On a related note though, I do expect 9-11 new-commers though. 4 we already know + 1-3 reserved for reveals to keep hype up + 4 kept secret.