A Diablo show isn't in the works, but the head of the series certainly likes the idea of one
An animated series was supposedly in development at one point in time.
No, there isn't a Diablo show coming, though general manager of the franchise at Blizzard Rod Fergusson has expressed interest in the idea.
It's becoming increasingly clear that live-action adaptations of video games are the big thing in film and TV. There had to be something after superhero flicks, after all, and how convenient is it that there's a wealth of IP just ready to be probably made worse when turned into a live-action project? Ok, sure, I do like the Sonic films, and the Fallout show was good enough that I might actually try playing the games again, but it's not like I wouldn't prefer there to be more original films and TV shows. Still, that won't stop them from happening, and while there isn't one planned right now, Rod Fergusson does at least think a Diablo show could work.
When asked about the idea of a Diablo show in a recent interview with Windows Central, Fergusson said, "Yeah I definitely think it could work. That's one of the things I really liked about Diablo as an IP, is that it's got very relatable themes because it's The High Heavens versus The Burning Hells, and that idea of Good versus Evil. I think that's something that could translate very well to something like that. You know, I wish I had something I could talk to you about today. But in terms of just the general idea, do I think it could work? I definitely do."
Interestingly, Fergusson pointed to Cyberpunk Edgerunners, the Netflix anime, as a series that brought him back to the game, saying, "Edgerunners was actually one of the ones that got me, the Cyberpunk [2077] anime. That one got me going back to Cyberpunk for sure. There's been a lot of great shows recently."
As noted by Windows Central, a soon-deleted tweet from Hellboy reboot writer Andy Cosby did note that he was in "final talks" to produce an animated Diablo series for Activision and Netflix, but this was way back in 2018, and there's been no word on such a project since then. Activision Blizzard is obviously in a very different spot now too, being owned by Microsoft and all, so maybe it will start looking into a Diablo series given how successful Fallout - which is getting a second season - has been.