The official Pokémon movie website has updated. Translations follow:

Masachika Ichimura Will be Playing the Legendary Pokémon Mewtwo!

Masachika Ichimura is returning as a guest voice actor
in "Mewtwo Strikes Back Evolution", which premieres Friday July 12th!
He will be playing the legendary Pokémon Mewtwo, just like he did in the first movie.

Ichimura gave us the following comment regarding his enthusiasm towards the second Pokémon movie he'll be appearing in,
as well as the Mewtwo role!

Mewtwo, the Pokémon that's a legend to everyone, is evolving further and returning once again.
This movie saw me waking my internal "Mewtwo soul" back up to perform the role.
This year's "Mewtwo Strikes Back Evolution", resurrected after 21 years, is the first ever Pokémon movie to be animated entirely in full 3DCG.
I want to bring the power of the legendary Pokémon "Mewtwo" to absolutely everyone...
both those of you that saw the first movie and those of you that didn't!
Come, come to the theater!

Those of you that can't wait for the premiere on Friday July 12th, check out the new trailer!
https://www.pokemon-movie.jp/movie/

Sources: https://www.pokemon-movie.jp/news/?p=3598