I've actually heard news about this quite some time ago, but now it's confirmed. Mewtwo is going to be showing up in the next Pokemon movie that's coming out in Japan along side the legendary bug, Genesect. According to serebii.net, Mewtwo is apparently going to face a sort of existential dilemma concerning the Genesect, as he is encountering artificial Pokemon like himself. Leave it to Mewtwo to bring deep complex issues to a kids' franchise.
The movie is also going to include a short featuring the newest Eevee form, Sylveon. The movie is set to come out in Japan in July. Of course those of us here in the U.S. will have to wait a bit longer.
