I just hope he writes his own story, and doesn't base it on any of the New 52 stuff. Both Gail Simone's Batgirl run and the current "Batgirl of Burnside" runs are pretty much the worst mainstream Batgirl stories ever published by DC. So, if he's doing Barbara Gordon (and there is 0% chance he'd be making a movie about the other Batgirl's, even though as a huge Cassandra Cain fan I'd love to see a movie with her), I hope he has his own story in mind and doesn't take stuff from anything recent.
One article said it will be based on the New 52 stuff, and if that's true I'll lose any real interest in the movie (I'll still see it, but I won't have any hope for it). Whedon's two Avengers movies weren't based on any specific stories (even age of Ultron was just some general Ultron stuff with mostly Whedon created elements), so hopefully he will be making his own Batgirl movie, not adapting any of the terrible recent comics.