It's actually hitting cinemas on May 10 according the Pokémon UK's Twitter.
NintendObserver’s select content on Pokémon: Detective Pikachu.
Ryan Reynolds in Ryme City.
First live action footage revealed right during the launch week of Pokémon Let's Go.
The entirety of the Pokémon World Championships 2018 livestreams. Though the press release says Pokémon Detective Pikachu is due for Summer 2019, the presentation explicitely announced the movie for next May.
Fans even got a chance to lend their voices to the film. Letterman led a chant of the attendees shouting out “Pikachu!” and “Charizard!” The audio was recorded for use in the movie.