Diablo Immortal will be released on June 2, Blizzard said in a video. The big surprise was that the game is coming to PC as well. So far, it has officially only been in the works for mobiles (Android and iOS).
It is as you probably know a free to play game, and there will be both crossplay and cross-progression between the platforms, allowing you to pick up and continue on PC where you left off on mobile. And vice versa.
The PC version should appear as an open beta, the website tells us without saying when. But there's a button to pre-register (unclear what the difference is to "signing up"...), so might as well do it if you're in the mood.