I bet a lot of Korean gamers will be happy to hear this; Blizzard is working on a sequel to the hit RTS StarCraft from 1998. Blizzard’s Paul Sams told IGN that they are working on at least 3 unannounced titles at the moment, he said,

“StarCraft is my absolutely favorite game of all time. As you probably already know, there is no doubt that we will continue the StarCraft and Diablo franchise, and trust me, I will be the happiest person in the world when we announce StarCraft 2.”

One of the other titles is Diablo 3, to which Blizzard is currently looking for new programmers and artists. This certainly buries the rumor one and for all, suggesting that Blizzard will only focus on MMOs.
In another interview with GamesIndustry, Sams said they are planning on a new WoW expansion every year, starting with WoW: Burning Crusade this fall. After that, every 12 months a new expansion will be released.