There's another interesting tidbit in Activision Blizzard's annual 10K filing
that mentions Blizzard is working on "sequels" to the Diablo franchise. Diablo III
is the only Diablo sequel that's been announced, so it's not clear if this means another Diablo game is in the works, if this refers to Diablo III DLC, or if they plan to release Diablo III in installments as they plan to with StarCraft II
(it also could just be a typo, but those are pretty rare in financial reports). Here's what it says: "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." IncGamers
contacted Blizzard with an inquiry about this, and were told: "We appreciate the interest, but we don't have any new announcements to make. For the Diablo franchise, our full focus is on Diablo III."