There were some major changes made to the X-Men mythos throughout the Jonathan Hickman's recent Dawn of X event, which essentially rebooted the continuity of the mutant characters in the pages of Marvel Comics. Under the leadership of a much more calculated Charles Xavier, all of the mutants in the known world moved to the newly-formed nation of Krakoa, existing peacefully together and working toward a better future. And when we say "all of the mutants," we quite literally mean all of them, as even the biggest villains from X-Men lore over the years are now joining the ranks of Xavier's nation, including Magneto, Sinister, and Apocalypse.
Some readers haven't responded well to the idea of everything just being fine between the X-Men and their former foes, considering just how many evil things some of them have done in the past. But getting every single mutant united for a common cause is truly the only way that Xavier and Moira could have succeeded. That's the picture that's painted in the books, anyway.
According to Hickman, who has written this entire relaunch, there's no better way to keep tabs on your biggest rivals than to have them working alongside you at all times.
"Hannibal was the best show on NBC over the last 10 years–always give the scene-eating cannibal a seat at the table," Hickman told Adventures in Poor Taste. "Especially if they can help you by doing things only they can do, even if in doing those things they might try and take a bite out of you. And why wouldn’t they? Mutants are delicious.
"Besides, what’s the thing that David Mamet always says? 'Whenever possible, put the monster under the bed, not outside the window.' (That wasn’t Mamet. I made that whole Mamet bit up. I’m honestly not even sure if it’s an actual saying or not.) (Whatever. It should be.)"
For the foreseeable future, all of the major X-Men villains will continue to work hand-in-hand, continuing to build a better life for all mutants around the world. Of course, something drastic will probably change at some point and more rivalries will be forged.