X-Men and the Fantastic Four will share the same universe, according to Mark Millar.
After the failure of the Fantastic Four's initial film outings, specifically the one which featured a pre-Captain America Chris Evans, it seems as though the franchise has come under grabs for whoever uses it next. Seeing as Disney and Marvel hadn't laid any claim to the famous foursome, Fox grabbed it and could be using the characters as part of the X-Men franchise.
After the Marvel Cinematic Universe grabbed the Guardians Of The Galaxy and tied it in with the Avengers films via Thanos, as previously reported by The Inquisitr, it only seemed natural that Fox would go the same direction after acquiring the rights to the Fantastic Four.
This further complicates matters for the comic book fans, since after Joss Whedon announced he would be using two mutants in the next Avengers film (as long as he doesn't refer to them as mutants), one long-time member of the X-Men franchise was once an Avenger as well. It seems as though teams are being split under studio rights, while other alliances are being formed.
Mark Millar states on the subject, "Without question I think you have to see some of these guys showing up in each other's movies. I think the most exciting thing in superhero movies, until The Avengers came along, was when Nick Fury showed up in 'Iron Man.' Even though it was a guy with an eye patch it was really cool -- and I expect we will see more of that."
The Fantastic Four and the X-Men have rarely appeared in the same comics, however. There was a stint where Storm appeared to be a member of the Fantastic Four (which technically meant that one of the original four was gone, otherwise it would be the Fantastic Five), and Dr. Doom fought the X-Men occasionally, but other than that, it could be a new trend in the canon as the films present it.
Perhaps some day we'll see the two teams combining forces to fight Galactus, and it won't be as disappointing as the Silver Surfer film was.
What do you think of the X-Men and the Fantastic Four showing up in each others' movies?