But how will that be any different that having more than one Dr Who, James Bond, Tarzan, Zorro, Superman, Batman, or Sherlock Holmes?
Doctor Who: A group creation, and still in its original continuity, despite the time gap between the old show and the new one. Shifting actors and writers have always been an integral part of the series. Nobody's original creation is being trampled here... in fact, the show has gone out of its way to preserve and acknowledge its origins.
James Bond: All the Bond movies made during Fleming's lifetime were based on his stories. He approved of the movies and did, in fact, actively make suggestions about them. They adhered to his vision, and it wasn't until long after his death that the franchise veered away into new territory, after having filmed literally every Bond story he ever wrote.
Tarzan: Burroughs could hardly wait to sell the film rights to Tarzan, and he got very rich as a result. They veered off his original stories, but he couldn't care less. He was a pulp writer, and... ka-ching!
Zorro: Another pulp creation like Tarzan. His creator, Johnston McCulley, took a similar attitude toward the movies (i.e., $$$!!). In fact, he liked Douglas Fairbanks's performance of Zorro so much that he actually based his own subsequent stories off that version.
Superman and Batman: Created for comic books, which by their very nature are shared by many writers and artists. It's true that Superman's creators got screwed, but years later they successfully sued for compensation.
Sherlock Holmes: Only two Holmes movies were made during Conan Doyle's life, which adhered closely to the spirit of his creation. The later Basil Rathbone ones, which placed Holmes in the 1940's and so forth, were made after his death and licensed by his estate.
If the franchise is strong enough, and I believe that it is, Buffy and the Buffyverse will survive a change of actors, writers, directors, and even the loss of Joss Whedon's input. The only matter worthy of any real concern is whether or not the quality of the finished product measures up to, or even surpasses the original, and that will not be determined until the movie is made. Until then, everything is just speculation and more or less educated guesses, flavored by a tremendous amount of emotionalism.
I guess I'm doomed never to succeed at convincing anyone that this is not a question of quality, but of principle. From my viewpoint, the "only matter worthy of any real concern" is that the creator of Buffy... the one who has been telling her story for 12 years while the Kuzuis sat on their asses and cashed paychecks... the only one who has ever made Buffy's a story worth paying attention to... is being excluded from his own creation.
If the Kuzuis were really concerned with making a good movie (they're not; they're interested in a quick cash-in -- Vertigo Entertainment exists specifically for that purpose), they would be working with the one person who's had success in producing and guiding Buffy stories.
Ian Flemming never had any input whatsoever on the making of a single James Bond movie. Edgar Rice Burroughs had no part in the making of any Tarzan movie. And though they did all star the same actor, only the original screenplay for the first "Dirty Harry" movie was written by the character's creator, Harry Julian Fink.
But none of those creators were cut out of the process, and none of them saw movies made with their characters against their wishes. If Joss had even so much as been asked for his participation or blessing in this project, we might be looking at a very different environment.
The Kuzuis had no part whatsoever in creating Buffy. They fronted the money to make a movie, which they proceeded to ruin. Their rights to the character consist of a piece of paper.
Well, maybe they ARE the only actors and writers capable of making a "real" Buffy story. One way or another, I want to know, and the only way that I will know is if this movie is made. So, if it's made, I'll go to see it. If it's crap, or if it's really good, we won't really know until then.
Do you really believe that the only gauge of whether a Buffy story is "real" or not is the quality? Because if so, I've read many good fanfics that should be submitted as "real" Buffy stories.
There seems to be a strong temptation here to use our potential enjoyment as a way of defining right and wrong. Sure, I knocked down that old lady and stole her purse, but I had fun spending her money. That's all that really counts, right?
(I'm not trying to accuse anyone here of villainy... just trying to convey how I view the situation.)