According to Nintendo Everything, Mewtwo Strikes Back: Evolution will be debuting in theaters in 2019. This information comes from a brief teaser in the Japanese release of Pokemon The Movie: Everyone’s Story.
Currently, reports in Japan state Masachika Ichimura will be reprising the role as Mewtwo. English audiences can likely expect Dan Green in the dub of the film, as Jay Goede (also known as Philip Bartlett in the credits of the first movie) has not since reprised the role. Dan Green provided the voice in Mewtwo Returns.
The teaser has yet to be posted online at this time.