The first game will consist of the Terran campaign and will be called "Terrans: Wings of Liberty". The second game, "Zerg: Heart of the Swarm" will concentrate on the Zerg and the third game will be "Protoss: Legacy of the Void".
"[The second and third games] will be like expansion packs, but we really want them to feel like standalone products," said Blizzard's Rob Pardo.More info at Shacknews.
Each campaign will be very different, with Pardo announcing the Zerg campaign will contain RPG elements. The Protoss campaigin will likewise be differentiated by elements of diplomacy. In addition, the Terran campaign will feature a Protoss mini-campaign.
The campaigns are planned as concentrated, epic storylines, with enough content to justify a full release. As a result, the games will now feature more in-game cinematics and story content.
Blizzard added that the plans for the multiplayer component are unchanged by the splitting of the campaigns. However, some units will now be unique to the campaigns and will not be playable in multiplayer.