I agree with people who want to see Diablo 4 return to a darker state but I'm not holding my breath. If nothing else, this last year Blizzard has shown that they're a corporation who now values money more than principles (not just the Hong Kong thing but last Blizzcon with Diablo Immortal, decisions made about all of their franchises over the last year, et cetera). Diablo 3 started rocky but turned into a mega commercial and critical success and I fear that they're going to look at how much money D3 has made, how it's still selling across multiple platforms, how it's still got an active seasonal player base, and figure that they will continue their D3 ROS design decisions in to D4.
As for Overwatch, I've long stopped caring about the game because I'm sick of the competitive design and constant changes. But if they were to announce a PVE expansion, a full-fledged, story based, game with decent replay value using all of the OW characters? They'd have my attention.