For fans of the Pokémon anime, Pikachu "talking" has always been pika-pika noise. And the voice of Pikachu has been Ikue Otani.
Yes, the Mystery Dungeon games have the Pocket Monsters talk to each other with in-game text. But this, this is just messed up.
The newest entry's latest teaser brings that to life with an anime trailer that features full voice acting-and not Otani's. In the trailer, that's Rie Kugimiya bringing the gum-flapping Pikachu to life.
For more on talking Pokemon, the Bulbapedia has a great rundown.