Blame both Disney and FOX for this one. . . .
A few years ago, Marvel and Sony struck a deal to incorporate Spider-Man into the Marvel Cinematic Universe, which was first showcased last spring for the release of Captain America: Civil War.
With the relationship between both companies looking to be promising for future films with each respective brand, Marvel soon worked out a deal with FOX last week to swap characters for upcoming movies, Deadpool 2 and Guardians of the Galaxy Vol. 2.
This immediately started rumors of the possibilities of the X-Men making a debut in the new MCU; however, the president of Marvel Studios quickly shut down those rumors.
In a recent interview, President of Marvel, Kevin Feige stated “It’s an impossibility at this juncture. We certainly have enough films to keep us busy for a number of lifetimes.”
So, at the moment, we don’t expect to see any direct interactions between the Avengers with X-Men or The Fantastic Four – at least until their dominance over DC Films weakens. In our opinion, this is a private issue between the Disney not wanting to jeopardize their brand at the expense of seeing the mature antics of FOX character, Deadpool in Avengers: Infinity War.
AMC Planning Price Hike for Blockbuster Movie Tickets
[Source]