WARNING: The following article contains spoilers for Marvel’s Ant-Man and The Wasp, in theaters now.
The ending of Ant-Man and The Wasp seems like it might have been designed to open up a doorway for the X-Men to be integrated into the Marvel Cinematic Universe, namely through the use of the quantum realm and its ability to cause mutations.
The entire future of the MCU is in a state of unrest as we wait to learn whether the Disney purchase of Fox's movie business (including the license to produce X-Men and Fantastic Four movies) will go through, a purchase which will open up the MCU to a whole pile of new characters. However, an interesting problem has always been, how do you work in characters like the X-Men into a world that does not have mutants?
Not only are there no mutants in the MCU, so far, past films have gone out of their way to make sure that no one could possibly be seen as a mutant, like when we learned that Scarlet Witch and Quicksilver gained their powers in Avengers: Age of Ultron through being experimented on with Scepter that Loki used in the first Avengers film (a Scepter that we learned contained the Mind Stone).
Meanwhile, over on Agents of S.H.I.E.L.D., they used the Inhumans and the Terrigan Mists to serve as fill-ins for the mutant experience, as the Terrigen Mists were unleashed on Earth and upon exposure to the mists, humans with Inhuman ancestry (whether they knew they had Inhuman ancestors or not) were transformed into Inhumans, often mutating them into grotesque beings in the process, like what happened to Melinda May's ex-husband, Andrew Garner.
Agents of S.H.I.E.L.D. began to treat Inhumans just like how mutants were treated in Marvel's comic book stories of the past. They were following a blueprint that Marvel Comics opened up with their Inhumanity event back in 2013, where the same thing that happened on Agents of S.H.I.E.L.D. happened in the Marvel Comics Universe. New Inhumans (or NuHumans) began to pop up all over the globe, just like mutants. Even some current Marvel characters who believed that they were mutants learned that they were actually Inhumans.
However, if the MCU could use actual mutants, it is likely that they would prefer to use them than Inhumans. The problem, though, is how do you suddenly introduce an influx of mutants into your universe? The answer, it seems, might lie within the Quantum Realm.