Blizzard plans to break StarCraft II into a trilogy of games focusing on the three factions and their stories: Terrans: Wings of Liberty, Zerg: Heart of the Swarm, and Protoss: Legacy of the Void.
The decision was made at the end of last year and nothing to do with the Activision merger, according to lead producer Chris Sigatay (talking to MTV Multiplayer). Apparently more and more cuts were needed to fit all of the stories into one game - something at odds with what Blizzard wanted to do.
The developer said expansions were something it always "intended" to do, anyway - now they're simply set in stone.
Terrans: Wings of Liberty will be the first game released, and Sigatay said there could be a year or more between subsequent instalments. Each game will feature around 26-30 missions and be a full, standalone product in its own right.
And while multiplayer will not require all three games to work, each release will seek to expand the options and units available - a similar sort of system to World of Warcraft and its expansions.
StarCraft II is due out sometime next year. Pop over to Eurogamer TV for a fancy new StarCraft II cinematic trailer.