I'm a 27-year old guy, and I read Twilight - along with my sisters and mother - and absolutely enjoyed it. Although the novels are aimed at teen girls, they also appeal to a broader range of readers. Of course, just like almost anything else, they're not going to appeal to everyone. Regarding the movie and its chances of success, I actually haven't personally heard of any overwhelmingly negative reactions to the film thus far; most of what I've heard has been positive, especially since the filmmakers have gone on record as wanting to strive to be as close to the novel as possible.
As to whether or not vampires have become the 'next big thing' in pop culture, vampires have always occupied a niche in pop culture, but the overall popularity of vampire-related material seems to fluctuate in cycles.