Fascination with vampires in popular culture has been growing steadily since at least the mid-1970s. People I know who are involved professionally with this stuff in terms of publishing, etc confess - at least the cleverer ones, IMAO, do - that they don't really know why. It's hard to guess whether the wave's crested or not.
It's possible to make some educated guesses as to why. Vampires spring from classical monster to pop culture phenomenon in the sixties, along with the sexual revolution and a more individual-focused society, both of which the vampire expresses nicely. Every decade deserves it's representative monsters, I think: the aggression and greed of the 80s saw the increase in popularity of werewolves, vampires returned to the fore with the self-involvement and identity exploration of the 90s, and the paranoia and siege-mentality of the noughties made it a fertile zombie decade. The thing with Twilight and it's knock-offs--I was discussing this with friends just recently--is that we can't figure out what, in the broader culture, it connects to. Being a self-mutilating emo douchebag doesn't seem to be any more sizeable a trend now than it has been since the nineties, the books/films' themes seem terribly retrograde... I don't know. Maybe it will become clearer in retrospect; it's often hard to identify movements while still in the middle of them.
Fictitiously yours, Trent Roman