I say that Saturn/MegaCD games will be pretty much out of the question, purely for the format they came on, and the very large filesizes in comparison to SD cards (one Saturn/MegaCD could take up a whole card). 32X is possible, though doubtful. Perhaps 'Chaotix will make it, purely for the sake of completing the retro Sonic set on VC.
Having said that, there are some Saturn/MegaCD games that do not take up the whole CD. I imagine, with abit of imaginitive editing and compressing, they could easily get, say, Virtua Fighter 2 down to a very friendly filesize. I think they could get it in the same area (filesize-wise!) as most N64 games.
But there remains alot of Saturn/MegaCD games that, without extreme porting time, wouldn't make the chop. It could be done, with alot of effort, though. Just look at the N64 version of RE2. A two CD games, compressed into a 64MB cartridge (each CD potentially holds 700MB!).
So yeah, I can see some 32X games making it (Star Wars Arcade is a very popular retro title, which had a good 32X port), but most of the more popular Saturn/MegaCD (especially Saturn) games, like massive RPGs and the like, just won't make it.
Unless they make it, but that would require considerable porting, which would then put those games far beyond the realms of a simple emulated ROM on the Revo, and would take much more resources, so I doubt it will happen. For the all-time classics, though, who knows? Maybe...