I can actually see a 3DS SSB. Technically, the console is powerful enough (judging from the looks of Kid Icarus, I'd say it's GPU is about on par with the GameCube, probably less but close), and with the addition of the slide pad, it would become possible to do Smash attacks. The only thing missing would be shielding with both the L and R buttons; presumably the R button would be relegated to grabbing. Taunting could be attained through the D-pad, attack with A, special with B, jump with X/Y, maybe a damage count and score on the lower screen, etc. Not to mention but it'd be pretty awesome to face people over ad-hoc wireless in addition to WFC.
In tl;dr format, it could work.
Besides the fact, during their E3 keynote this year, I noticed a Maxim Tomato in the background of the final video they showed. Could that be an indication of things to come?