there's a bunch of marvel players that started off as smash players so i can see them going back. hopefully the game is pretty good competitively so other pros pick it up.I don't see Smash 4 taking over the scene because the other Smash games haven't done so despite having larger turnouts. Plus much of the fighting game scene is still segregated from the Smash scene.
I do expect to see Smash 4 at more events with fighting games since it will be easier to run on a modern console without having to deal with CRTs, but ultimately it will depend on how well the game does competitively.