Director Matthew Vaughn's X-Men: First Class was, in many respects, part origins movie for young Erik Lensherr/Magneto (played by Michael Fassbender), with a script that had absorbed story elements from the cancelled X-Men Origins: Magneto project. Similarly, the plight of the young Charles Xavier/Professor X (James McAvoy) provided an emotional core for the larger-scale proceedings in director Bryan Singer's First Class followup, X-Men: Days of Future Past.
So, will the upcoming X-Men: Apocalypse - the conclusion to the First Class trilogy that will once again have Singer at the helm - finish the cycle by shifting its attention to Raven Darkholme/Mystique (Jennifer Lawrence), who's shared protagonist duties with Erik and Charles in the First Class series thus far? Going by the recent comments from Apocalypse co-writer/producer Simon Kinberg (who also scripted and produced Days of Future Past), that might well be the case.
Kinberg, during a recent interview with Collider, reaffirmed that Apocalypse is being designed to bring a sense of closure to the story that began with First Class, while also marking the "completion of an arc" for the main characters in First Class and Days of Future Past - Erik, Charles, and Raven in particular, as mentioned before. He also informed Collider that Apocalypse will continue to explore the dynamic between Mystique and young Hank McCoy/Beast (Nicholas Hoult) that was established in First Class.
"... I think that the friendship between Erik and Charles, which has always been so integral to the franchise, is something we’re continuing to explore and hopefully deepen with Apocalypse. And the relationship between Beast and Mystique is a really interesting one that we didn’t have a lot of time to explore in Days of Future Past, so we’ll have an opportunity to do more of that in Apocalypse.”
The Apocalypse storyline is still being shaped by Kinberg and Singer, in collaboration with X2: X-Men United co-screenwriters Michael Dougherty and Dan Harris, so certain aspects (such as the "emotional core" of the narrative) have yet to be nailed down. That said, between his mention of the Mystique/Beast relationship and his thoughts on the impact of Charles and Erik on Raven (see below), Kinberg's comments seem to point in the direction of a more Mystique-heavy story. (As was brought up before, this would also make sense, in terms of the First Class series' thematic progression.)
“Part of what’s really interesting about Mystique’s character is that she is, in some ways, the child of both Erik and Charles. She grew up with Charles and then she sort of became a woman with Erik, so her being the cross-pollination, if you will, of those two philosophies and those two men is something we can explore in the movie too.”
Both First Class and Days of Future Past juxtapose their more intimate character storyline with massive global conflicts, and Apocalypse - as indicated by the subtitle that refers to the powerful mutant of the same name - will be in keeping with that practice alive. That will hole true even if Mystique's journey does wind up serving as the "heart" of the film (and the movie winds up being "hers" like First Class was Erik's and Days of Future Past's was Charles').
Kinberg, in the same Collider interview, teased that the Apocalypse team are "having a lot of fun" with incorporating the 1980s setting of the movie into the storyline - not to mention, the process of planning out the feature's huge action and immense scale.
“There are some very big set pieces. I don’t know what the budget’s gonna be because we’re still a ways away from budgeting the film, but I can say that Fox has a lot of creative confidence in the team that made Days of Future Past—myself, Bryan, Lauren Shuler Donner, Hutch Parker. All of those people are coming back so in terms of a sandbox they’re definitely giving us a lot of room to play creatively and take chances the way that we took some chances on Days of Future Past, and do some radical things just as I think we did some radical things in Days of Future Past.”
20th Century Fox is going to release the long-awaited Deadpool movie in theaters before Apocalypse arrives on the scene; a third Wolverine solo feature is scheduled to arrive a year later, and it's possible that other solo X-Men films (see: Gambit) could also be made down the line. Similarly, a Mystique spinoff is something that has been floated as a possibility, and a more Mystique-focused Apocalypse could be a nice trial run for how such a film might play out. We'll see what happens, though.
Deadpool is scheduled to hit theaters on February 12th, 2016, followed by X-Men: Apocalypse on May 27th, 2016, The Wolverine 3 (not the official title) on March 3rd, 2017, and some as-yet unspecified X-Men film on July 13th, 2018.