It will be something like Destiny / Anthem (That new bioware game)... coop based open world mmo/arpg loot hunter.
Probably in third person view - Hopefully with the ability to zoom the camera in/out.
Destiny occupy the scifi part of the genre and Diablo will cover the fantasy / dark fantasy side. That way Activision Blizzard can pretty much take over the whole genre... Unless Destiny 2 will suck and Anthem will be good which i doubt (Both of them will suck ).