If I'm remembering correctly, no Sega console has more buttons than the N64. So there's no issue there. However the Revolution is able to allow control for NES, Super NES, N64, GameCube, and Revolution games, it probably wouldn't be too hard for the Master System, Genesis, 32X, Sega CD, Saturn, (and maybe even Dreamcast) games.
So the issue would be technical, though I think that's minor (assuming the later Sega consoles didn't have some crazy and unique thing that's too bothersome to emulate) and whatever marketing and property rights there are to get in the way.
Unless Sega's going to come back with hardware of their own one day (which seems unlikely), it seems like Sega should, or bring it up with Nintendo, if they haven't already. Other than Fantasy Zone or whatever on the NES, Sega hasn't had a game on a Nintendo console until the GameCube, so it's not like they would already be talking about other software.
I've grown up with Nintendo games since the NES, so while the rerelease and official emulation of old games for Nintendo systems is sweet, there's a good chance I've played them several times over before. Having Sega games as well would allow a former competitor's past to not fade away, and then every gamer around or over the age of 20something would have a nostalgic reason to pick up a Revolution, no matter what they played in the past (assuming they weren't, like, Turbo-GrafX-16 or CD-i or 3D0 fans or something).
Plus, if they don't, there's always the possibility that Sony or Microsoft might steal Nintendo's retro-thunder by getting the rights to the Sega library and having a game download service of their own. A monopoly on old games would really ensure a Revolution in every nostalgic gamer's home.