I wasn't exactly referring to newcomers, I was referring to veterans primary.
Assuming that Snake/Squirtle/Ivysaur were to be cut and the rest of the Brawl roster to return plus the 6 newcomers we'd have a roster of 42. If we were to keep it at that number there would either be no more newcomers and or several veteran characters would be cut.
Adding the most likely veterans (Falcon, Wario, Ness, Lucas, Ice Climbers) and newcomers (Palutena, Pacman) to the current roster of 29 we'd be at 36 characters. Assuming 42, depending on newcomers, (Meta Knight, Ganondorf, Ike, Falco, Wolf, ROB, G&W) 2 of these veterans would have to be cut, which could go even higher depending if you want to have any extra newcomers.