There's both Diablo Immortal and Diablo 4 guaranteed on the horizon, with a potential revisiting of Diablo 2's story in a remastered (nay, Resurrected?) version.
Before the coming of the Nephalem, Imperius was the unquestioned greatest warrior in all creation.
Diablo 3 left some pretty big loose ends that aren't getting tied up any time soon.
Last week we covered Diablo's plans for Khanduras and Tristram.