nah, anon. brawl was about 6.77 gigs on the wii disc, and the 3ds cartridges are confirmed to hold up to about 8 gigs of data

considering they're not putting in a traditional "story" mode, that frees up more memory

and with street fighter 4 and tekken 3d for the the 3ds both having 30-40 characters in it, i don't see them really limiting characters just because of the 3ds