In a recent interview with IGN, Jennifer Lawrence discussed where we will see Mystique in X-Men: Days of Future Past. At the end of X-Men: First Class she joined Magneto, but that's not where we'll find her in the upcoming sequel. Here's what Lawrence had to say when she was asked about it,
"We find Raven, she's split off from Eric and Charles and she's kind of her own agent. She has one mission of trying to assassinate somebody and it will be her first kill basically, and because we've seen her in the future and what she becomes and this is kind of a turning point for her."
X-Men: Days of Future Past opens May 23, 2014, and it stars Hugh Jackman, Ian McKellen, Patrick Stewart, Michael Fassbender, James McAvoy, Jennifer Lawrence, Nicholas Hoult, Halle Berry, Anna Paquin, Ellen Page, Shawn Ashmore, Peter Dinklage, Omar Sy, and Evan Peters.