Always figured they would be back, they're a neat part of the game. It surprised the heck out of me the first time I got infected in Morrowind, which I think was on a second playthrough, I had no idea there even were vampires my first time playing. I could be wrong about this though, but I don't think Oblivion had any actual quests purely for vampire players other than curing yourself. Morrowind had 3 or 4 that only opened up once you turned, working for other vampires, killing vampire hunters, that kind of thing which let you earn a few extra items you couldn't get as a normal. Hopefully they'll bring a few missions like those back so there will actually be a reason to go through the trouble of being infected.