Vvardenfell sank, so i believe it took all of its funky critters with it.
Cliffracers can fly, though... besides, according to rumors we've heard, there weren't any cliffracers in Vvardenfell at the time of the eruption. And the rumor specifically says they were DRIVEN FROM Morrowind, which makes me think they weren't all killed, just driven away, which may mean that they survived somewhere else in Tamriel, or it might be that they couldn't survive wherever they were driven to, and went
But anyway, cliffracers are not dragons at all, just because something can fly and looks reptilian doesn't make it a dragon, really, they look more like pterodactyls to me, pterodactyls with no legs... yeah, I don't get why they have no legs either. Not only are they not dragons, they're not even very similar. They have no legs (Elder Scrolls dragons have two legs.) they aren't intelligent (As far as we know.) they don't have a language or writing system (Which the dragons in Skyrim do.) they can't breathe fire or use dragon shouts or anything, they also don't really look like dragons, and really, there's no reason why they would be in Skyrim except to torment people, as I doubt clifracers are suited to surviving in Skyrim's climate. So no, I don't think they'll appear in Skyrim, and I don't want them to, cliffracers are something I'd rather not have to see in another game.