Has Blizzard been working on much besides Overwatch updates and content? WoW expansion came out this year I think too? Probably some Hearthstone stuff too.
Overwatch League is the worst thing to happen to that game and Blizzard's priorities. Starcraft 2 was pushed as a very competitive game by Blizzard, but it didn't feel like all their energy went into fostering a competitive community, unlike Overwatch.
Who knows, all I know is Diablo 3 is nearing being 7 years old and some sort of sequel or remake coming out towards the end of this gen, when there's millions of consoles out there, seems like a safe bet financially.
They're working on D4. They've been filling a bunch of internal positions that have been advertised for "unlisted diablo project" so yeah. The mobile game is done by another Dev using assets that already existed; maybe they got some help from Team 3 members but if they did it wasn't a lot and that team is in maintenance mode anyway with not a lot to do unless they're working on D4.
I actually don't HATE that this exists, but Blizzard is increasingly tone deaf to what their fanbases want, Diablo fans in particular. After the not so great D3 launch and everything that came with it (auction house, perceived shittiness of the game's mechanics compared to D2, butthurt fans that got a sad because Deckard Cain got killed, etc etc) announcing this before D4 is super dumb. Especially because the big rumor heading into Blizzcon 2 weeks ago was a D4 reveal, but then that got toned down to "probably a HD D2 remake" which riled up that SPECIFIC section of the fanbase that loved D2 so much, then to give them this instead... I'm not saying they're not lunatics, but I understand where they're coming from.
People that have actually played the game seemed to like it ok for what it is, but it seems more focused on multiplayer almost to a necessity which I dislike, and I don't like gaming on mobile other than menu based rpgs, so I highly doubt I'm going to play this. I feel kinda bad for Wyatt Cheng, he's the closest thing to a Diablo founding father still left at Blizzard and had to announce this, lulz.