While the rights to the X-Men and the Fantastic Four both currently belong to 20th Century Fox, they don't actually exist in a shared universe. As we learned last year thanks to writer/producer Simon Kinberg, the characters audiences will be introduced to in director Josh Trank's new film actually exists in a parallel reality to Wolverine, Professor X, and the other mutants - which is why you won't soon be seeing them interact on the big screen. But while this barrier does exist, the truth of the matter is that this idea does absolutely nothing to stop an X-Men/Fantastic Four crossover, as the plot device to get it done is actually right at the center of Trank's new movie: inter-dimensional travel.
Recently speaking with the New York Daily News, Simon Kinberg doubled down on his earlier comments about the franchises - saying, "The Fantastic 4 live in a world without mutants, and the X-Men live in a world without the Fantastic 4" - and while the newspaper took this as denial that a crossover could ever happen, that's very far from the truth. The reality is that characters existing in different universes is a small hurdle to get over when you can just throw advanced science-fiction theories at the problem. In Josh Trank's Fantastic Four, every single main member of the cast is actively working to figure out how to hop from one dimension to another, and this technology could easily be used in a future adventure that winds up seeing the team traveling to the world that does have the X-Men in it.
Of course, when one looks at Simon Kinberg's recent comments with a more skeptical eye, it's pretty easy to understand why the writer/producer may want to make it clear right now that the X-Men and Fantastic Four are distinct franchises. Josh Trank's movie about Marvel's first family is arriving in theaters this weekend on a gigantic wave of bad buzz, as most critics have not been kind to the film. As a result of this, if Fox ultimately decides that they don't want to move forward with this incarnation of the team, it doesn't take a lot of heavy lifting to make sure a distinct line drawn between the two comic book movies series. At the same time, as mentioned earlier, there is an obvious door that is kept wide open (a door that Bryan Singer has recognized as existing).
The next few weeks should be full of interesting updates about the potential future of the Fantastic Four as a film franchise - and a big part of that will be talk about whether or not an X-Men crossover could still be on the table. At this point we still don't know if it's actually ever going to happen, but the reality is that it wouldn't be hard at all for Fox and the creatives behind the movies to get it done.
