At some point, Blizzard considered doing another expansion for Diablo 2 and developing a different version of Diablo 3.
Diablo 2 developers were designing another expansion for the game, one of the game's developers revealed. The expansion was only designed and never produced, David Brevik, the co-founder and president of defunct studio Blizzard North, wrote on Twitter. "I had a multi-page design doc going over new classes, new areas, new mechanics and story concepts," Brevik said. "That's as far as it got."
Brevik also noted that he designed the second expansion around six to 12 months before leaving Blizzard North. "This is one of the reasons it was never made," Brevik added. "It was before the 1.10 patch (in terms of timeline). We were also working on our version of Diablo 3 at the time, plus another unannounced project."
The developer also shared details on another version of Diablo 3 they had in mind which would have been different from any other Diablo. "I think it was really interesting. We used a lot of the game-structure concepts for Marvel Heroes. I was an ARPG+MMO. MMO in terms of many people playing at once, not like WoW. It was scrapped because most of BlizNo left."
UPD: Originally, we made a mistake saying that the second expansion was planned as "ARPG+MMO". This formula was actually a base for another version of Diablo 3 according to the developer. We apologize for the original misleading headline.