This may be a special situation. Marvel wouldn't want to be perceived to be "fixing" the Johnny Storm casting.
Add multiracial families to the list of things America just isn't ready for.
Fantastic Four is at 14% on Rotten Tomatoes which would put it even with Howard the Duck and ahead of the worst rated Marvel movie ever by RT, Elektra. Marvel may be getting FF back in time to jumpstart Phase 4.
http://www.rottentomatoes.com/guides/marvel-movies-worst-to-best/