(If this should be under Modern, please move it.)
Okay, having seen the 1979 version of Nosferatu numerous times since the turn of the century, I kinda have this weird desire to see what became of the vampirized Harker. Maybe I'm the only one, but a sequel in some form would be interesting to see if someone were to stake him or something. Maybe he'd go back to Wisborg and it would become a remake of The Secrets of House 5 (now there's an obscure movie!).
Well, not quite what you're looking for, but there was a sorta / kinda in name only sequel, Nosferatu in Venezia with Klaus Kinski (NOTE: Contains nudity - not for work):
http://www.youtube.com/watch?v=wEtDo6OPw2s# (http://www.youtube.com/watch?v=wEtDo6OPw2s#)