A SEC filing by Activision hints that maybe more then one Diablo title is in the works.
The document details Blizzard’s currents plans within the company.
“Blizzard is currently developing new games, including a new expansion pack to the World of Warcraft franchise, Cataclysm, StarCraft II: Wings of Liberty, which will be released with the new and improved Battle.net, and sequels to the Diablo franchise.“
If you didn’t notice, the text details “sequels” with an “s” to the Diablo franchise. What exactly does that mean? I have no idea. It could simply just be an expansion to Diablo III as pointed out by CVG.
I have a feeling we won’t be finding out for quite some time considering Diablo III won’t be released for some time, but maybe we will get another spin off title along side or soon after Diablo III.