Funny you should mention porting SEGA games because there's a Sonic the Hedgehog ROM floating around the net that is supposed to work with SNES emulators. I haven't tried it, myself, because if I want to play Sonic I'll fire up my Genesis or GameCube (I have the game for both). I don't know what the origin of the ROM is, but I would suspect one of the following: a leaked port SEGA made to hedge its bets, a fan done port (changing the Genesis ROM in whatever ways necessary), or a fan done rip-off (built up from scratch using only the sprites from the Genesis version). Of the preceding, honestly, the first would be the biggest surprise to me.
So it is possible, but certainly more trouble than it's worth, as Ian noted. Especially since multiple searches on Google indicate that there are emulators for every system SEGA ever made, including GameGear, SegaCD, and the 32x (Genesis addon). And all of them were made without the detailed technical knowledge that engineers at SEGA would have at their disposal. Many of them are also open source, so SEGA could even piggy back their effort.
That said, even though it would be nice for SEGA to do this, they would likely also bring their emulators and such to the other consoles to maximize their own profits. Since all the next gen consoles will be PowerPC based, it should take a minimal effort on SEGA's part. I wouldn't, therefor, count on it becoming a Rev advantage, if it's done at all.
BlackGriffen