The X-Men have their own cinematic universe that they get to do whatever they want in but that doesn't mean that some of the actors don't want to play in a bigger sandbox. With a future in the X-Men franchise extremely unclear at this point, Jennifer Lawrence wouldn't say no to appearing in a Guardians of the Galaxy sequel, one the most popular series in the MCU. She's even offered to bring her X-Men character Mystique over so she can meet some other people who have to put makeup on for a couple hours.
Oh my god, I would love to. I would choose that over doing another X-Men movie maybe. I won't be Mystique in the X-Men movies, but I would love to be Mystique in the Guardians of the Galaxy. I wonder if that can happen?
Two years ago, I would have said "No, Jennifer, it can't happen," but Spider-Man going to the MCU was also something that people once thought couldn't happen. After the landmark partnership between Marvel Studios and Sony that allowed an all-new rebooted Spider-Man to star in Avengers films, the threshold of possibilities has widened considerably. While arguing if the X-Men will ever join forces with the Avengers is a battle for another time, the deal with Spider-Man has been working out well for Sony so far.
I'm not against the idea of a Jennifer Lawrence cameo, but maybe it's better to leave Mystique wherever she is. Fox has attempted to make Mystique a pillar of the X-Men franchise in accordance with Lawrence's own rise to power and that has worked to mixed results. The shapeshifting mutant was at her peak in X-Men: Days of Future Past, but took some major steps back in X-Men: Apocalypse. Lawrence's lack of enthusiasm to "blue up" and play the character was pretty apparent in that film and seeing her in Guardians probably isn't too high on many people's lists.
Of course, this is just the sort of banter that comes out in the long gauntlet of press junkets, so it shouldn't be taken too seriously. Here's the clip of the MTV interview and everyone can see it for themselves.
The X-Men and space go hand in hand so let me ask you all this: what element from the X-Men would you most like to see in a Guardians movie? Do I hear the Shi'ar anybody?