https://www.pcgamer.com/blizzard-is-working-on-a-new-unannounced-diablo-project/

Ahead of BlizzCon 2017, Blizzard said there would be no Diablo-related announcement at the show. "There will be a time for that at some point in the future," community manager Nevalistis explained, "but that time is not now." It appears to be approaching, however. Multiple job listings on the Blizzard careers site say the studio is seeking environment, technical, and "dungeon" artists for a new Diablo game. 

"The minions of Hell are growing stronger," the Dungeon Artist listing says. "We're working on a new, unannounced Diablo project. Are you a skilled Dungeon Artist? Come work with us, and together we will build something exceptional."