I'd like to bring this up again:
Like Brawl's roster additions they simply push characters to the side. With this in mind
if there are any more characters than the ESRB leak shows my only expectations are...
Star Fox / Pokemon / New Single Series / New Clone.
Now let me explain why. The roster placement when adding characters pushes characters to the left or right. Now look at the ESRB leak roster, say you added a character to DK series that would push everything on the right over meaning Metroid would have to go down splitting Samus and ZSS or leaving a gap in which case little mac would not move up either. Look at who is to his right and left since E3 it's clear they thought about the final layout since then, him and game & watch are single rep series being preemptively used to fill in blanks.
Star Fox / Pokemon / New Single Rep because adding any of these can still keep the roster perfectly organized in the same way that it is right now. On the other hand a single clone can be added and be no problem.
Hopefully that's enough in explaining where I'm going with this. This goes under the assumption the roster will keep series in line without splitting them and that characters won't suddenly warp about. (They did not in Brawl, only pushes aside.)