They are not gonna make a new game on the foundations of Diablo 3 where the game itself can't even work proper. You'd have to be completely insane if you think they're putting a HD remake of D2 right after the opening ceremony ahead of Overwatch, their prime cash cow.
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Unlikely since we got a few patches after the RoS release and then they doubled down on their crew. Diablo 3 has been running in maintenance for years because they shuffled their main diablo crew over to their new project. Blizzard already knew Diablo 3 wasn't sustainable on the engine it's currently running