I'd like to bring to your attention that there's no way Pokemon Switch is coming out before this movie is released. They're not making this movie 'for fun', it's obviously meant to help raise awareness of the Pokemon franchise like Pokemon GO did and thus increase sales of the Switch game. Similar to how Kingsglaive was made solely to market Final Fantasy XV.

Releasing a big feature film that will be seen by millions of people AFTER the game is released would be an incredibly huge loss and I don't think even Nintendo are capable of doing something so stupid. Their plan is likely to release the movie in the fall of 2019 with a tie-in marketing campaign, with the game being released shortly afterwards in time for Christmas.