Mr Trick
Scooby
Exactly.
Not to mention the 1000lb gorilla in the room. What would a Buffy (current universe Buffy) be like without Angel and Spike. Both Boreanaz and Marsters have said they can no longer play the vampers (even if they wanted) so their exclusion, even if written off, would still be the element to take you out of the movie. I do not believe, unless you reboot it, you can have a Buffy movie without either Angel or Spike.
Then of course, the possibility that Nicholas Brendon could have difficulty getting and keeping his part, you might have a Buffy movie without Angel, Spike and Xander. So... yeah, I think Sarah saying she is too old is a way to say it wont happen.
But isn't that a bit like saying that Angel couldn't have his own show without Buffy? Buffy was always an indeperndent character. Yes those two became bit parts of her narrative, but the show could go on with or without them.
I have some doubts over whether SMG can still play Buffy, but at the same time I don't think anyone else should play her. And if that means no movie, then so be it.