From the job listing, "We're working on a new, unannounced Diablo project. "
Old News. Jobs Postings for this are up for more than a year, AFAIR.
With our luck this "unannounced Diablo project" is probably some in-game cosmetic reward for Overwatch.
Wasn't this confirmed a while back when someone accepted a new position for an "unannounced game" and then the same dude took to twitter saying he was happy to be joining the Diablo team?
9 positions opened under unannounced game / diablo.
25 positions opened under just unannounced game.