Yes and no. Yes because the Ayleid aren't dead. They've fled to Valenwood and High Rock. No because the Ayleid are dead as a people. The people who fled have been assimilated. So while there might be mer like Umaril, the Ayleid as a people are long gone. Even the ones that didn't move out of Cyrodiil supposedly have become the Wild Elves.
It all depends on what you do. Though I don't think people are asking for the return of yet another Ayleid villain from Oblivion.
Dont forget the Wild Elves. They didnt became assimilated by other cultures - of course, their culture is nothing really Ayleid anymore, either, most likely.
So, uh, yes, the Romans example is best. Could somebody come and unite all the Romans nowadays? Err... (mind, pan-romancist romantic-ultranationalist movements existed, particularily in the 19th century, but thats really crazy fringe).