Starcraft has shipped 9 million copies the last time I checked. Also, Blizzard is developing Starcraft: Ghost in conjunction with Nihilistic – the same developer that made Vampire: The Masquerade - Redemption. I’m not surpirsed that Blizzard isn’t developing the game alone, as it has its hands full bringing gamers World of Warcraft.
I expect that Starcraft 2 will be the next game on Blizzard’s list above Diablo 3 and Warcraft 4.