The 20th movie in the Pokémon franchise, dubbed “Pokémon I Choose You”, has just received its first trailer. The trailer honestly doesn’t show much more than what you’ve probably already seen. It is also in Japanese, as an English version has not yet been released.
Looks like Ash goes back to his roots when Pokémon I Choose You releases in Japan on July 15th, 2017. Other dates have not yet been announced for the worldwide release, but it’s generally 4-6 months after it airs in Japan. I would look for a November/December release in the United States.