Of all the top-line superhero franchises committed to the silver screen, none has been as horribly mangled by misuse than the Fantastic Four.
The quartet of Mr Fantastic, The Invisible Woman, Human Torch, and the Thing were once among Marvel's core characters. In recent years however, partly as a result of the increasingly dire movies about the foursome, their stock has fallen to the extent the comics universe has dismembered and dispersed the group.
It's possible Marvel is deliberately devaluing the FF until 20th Century Fox divest themselves of the movie license, so Marvel can do whatever they want with it again.
If that happens, the Fantastic Four could find their way into the Marvel Cinematic Universe, rubbing shoulders with the Avengers, Spider-Man, and all the many denizens of the MCU incoming in the near future. The danger is, of course, that the FF will continue to suck, and bring the MCU down with them.
Some cunning filmmaking could help ease the FF into the rest of the MCU in logical and cool ways, without having them turn up out of nowhere. It won't guarantee they'll reverse decades of cinematic misuse, but it would be a damn fine start.