It's not certain how wide the launch will be on June 21st. Niantic had to make some Pokémon Go players wait weeks or even months to start playing.

There's probably a good reason for the staggered approach. Pokémon Go is still popular long after the initial phenomenon wore out, and now Niantic is introducing a similarly location-based game that has the full weight of Harry Potter fandom behind it. You can be sure there's plenty of pent-up demand. If there's any uncertainty, it's whether or not Wizards Unite will repeat history in the long run and thrive well after the initial fad is over.