I disagree. If Guardians of the Galaxy could be successful, there's no reason Inhumans can't be a movie. But its foolish to claim it would be a movie 'franchise'. There isn't enough material. But it isn't stand alone, either. The Inhumans would always have to fit in the larger Marvel Universe, whereas the mutants have been allowed a much freer rein.

Asking why Marvel keeps upping Inhumans instead of mutants is like asking why does Marvel keep promoting Iron Man instead of Superman. They don't control that product.