I think its going to expand to 10 columns and the clones will shift up to their franchises like they did in Melee. Pokemon has been known to shift around, too, it happened in Melee, so I wouldn't be surprised at all to see it shift down.
I think we've got about 6 characters, personally, MAYBE 7 if they add a character to the final row, but its a stretch. The final row hasn't gotten extended at all, so perhaps its for Mii Fighters.
I definitely think we've got the Hype 3. If the roster extends to 10 wide (which I think is most likely), we've probably go both K. Rool and Dixie Kong. A Zelda newcomer? Maybe. Isaac I still think is in as well, and also Wolf.
So, my thoughts in order:
1. Wolf
2. Ridley
3. Mewtwo
4. King K. Rool
5. Isaac
6. Dixie Kong
7. Impa
Naturally, if it turns out we've got less, I'd cut from the bottom of the list first, so Impa, then Dixie, then Isaac, Rool, etc. Unless one of them is disconfirmed outright, which so far hasn't happened.