To comment on my age comment. It is true that if they left time between S7 and the movie age would actually make sense. David would be fine, he is more in shape in Bones then he ever was on Angel. (Bones is amazing by the way lol). But even with make up, James looks very old. I am not ragging on him, but from S6 he looked in his twenties and S7 looked like his forties. In the new DragonBall Z movie he has head to toe make-up, so I think that would be tricky. NB looked aged as well and so did AH, but not being Vampires, it doesn't really matter.
Buffy could be done so much better with new technology. Watching television alone special effects are amazing. Terminator, Supernatural, the short lived Bionic Woman, all had amazing effects and fight scenes. For a Buffy movie they would have to use such amazing effects, excellent fight scenes, upping the notch to modern cinema. Even though Buffy fans don't care, for the movie to be successful this would have to happen. The script would have to be an amazing stand alone story, for non Buffy fans, as well as satisfying the apitites of us die-hard lovers of the characters. So for the movie to be a success in my opinion this would have to happen:
Breath-taking special effects
Believable cutting-edge monster make-up
Impressive fight choreography
An Epic story plot
The characters would have to have their loved personalities shine through an captivate the people who don't know them yet
The characters would have to stay true to who they were to the show (no drastic personality differences do to "situations that occurred from when we last saw them")
It would have to incorporate intense action, suspense, a compelling story line as well as the drama and character based uniqueness of BUffy. We need it to be good for everyone, men, women, old, young, Buffy fans and none Buffy fans.
It would have to be funny, using allot of modern pop culture references
It would have to do all of this without losing it's Buffiness. The witty dialogue, the interesting characters, and the qwuarkiness would all have to still be there.
I think it can be done. It would have to happen soon again because of age. Although it can't be rushed. But I don't think the time between the TV series and the movie really matters. They are making a Dark Shadows movie, a Dragonball Z movie, they just made the X-Files movie, Star Trek, etc.
I hope it happens...probably won't. But we can dream!