When I first entered this thread I answered "7-8" on the poll for how many newcomers there would be, and I'm still in the same mindset. Even after Sakurai mentioned "not to expect too many characters", I think 8 is reasonable. Less than usual, but still a good number, I'm thinking 5 full characters and 3 Echoes. So 4 more full characters and 2 more Echoes.
If I were to guess who those characters would be I'd say:
1. Simon Belmont (I think enough information has come out to at least consider that Vergeben's leak is true)
2. Rayman (Nintendo and Ubisoft have been playing really chummy with each other, and he already sort of has his foot in the door)
3. Mimikyu (I know Pokemon already has a lot of representation, but next to Mario it really is Nintendo's bread and butter)
4. K. Rool or Ashley (as far as I can tell, these 2 are the most requested after Ridley. Could be one, could be both)
E1. Shadow (not necessarily because he hasn't been seen as an AT yet, but because Sonic is a popular franchise with a long history with Nintendo, Sega and Nintendo seem to be closer than ever, and Sonic is now a two time veteran, if any third party is going to get a second rep this time it's Sonic)
E2. I really don't know. Part of me wants to say Black Shadow because F-Zero is the only original franchise (not including Yoshi) that still only has one rep and part of me wants to say Medusa or Viridi because Sakurai obviously loves Kid Icarus.
I just don't think Dixie will be an Echo because the jetpack makes no sense for her. Sorry, I didn't mean to type this much.
Edit: I should point out that I left Inkling out of my thought process, partially because I forgot while typing this and partially because I had thought of the poll as "how many newcomers yet to be revealed" and I stumbled in after the original reveal trailer.