Nosferatu? Are you referring to the Remans because they are simply a seperate species from the Romulans, and they are in no way replacing normal romulans. As for the new movie, Nero and his minions don't even appear to have ridges.
Has it been established that Nero is, indeed, a Romulan rather than being in league with them? When the first pictures of him emerged, I recall Abrams or another producer commenting on the lack of ridges by saying 'there's a reason for that' or something along those lines.
Fictitiously yours, Trent Roman