I think the world's geek population, myself included, would have a collective heart attack! All jokes aside though, I think this would be an amazing pairing. Joss has proven that he can kill it in space, Firefly is living proof, and he has proven he can kill it with blockbuster franchises like The Avengers. He has an established and loyal following. It seems a natural thing to me, particularly if the schedule align, which they seem to do.