In an interview with Diablo fan sites about his new novel, Knaak stated that he was "not writing for a dead game." When asked to clarify if he was referring to a Diablo sequel, Knaak added, "I am not writing for a dead world...but a world with dead. nuff said."
The folks at Shacknews have probed "multiple reliable industry sources close to Blizzard" about the subject, and based on the information collected, they say they can confirm that Diablo 3 is indeed in development.