Gamestop's listing turned out to be false:

• In an interview, lead designer Dustin Browder admitted that they want to release in '09 (we think in time for Christmas), but the release date depends on the success of the beta as they won't release anything that isn't fully finished.
  
• UK release date, according to amazon, is 9/26/09.
• Gamestop listed the game as being available on 6/2/09, but this turned out to be false.
  
• Some SC2 system requirements available
  
• Includes three games, Wings of Liberty (Terrans), Heart of the Swarm (Zerg), and Legacy of the Void (Protoss) with the second two games being considered expansion packs
• Wings of Liberty will be released first; no release date has been set
• Each game features one race and includes 26-30 campaigns
• Developers hope to release the expansion packs within one year of each other
• Each game will complement the others, but one will not be necessary to play the others for single-player
• BUT each game will have specific units that will require you to own that expansion pack to utilize for multi-player
• A beta version of the game will be released in the near future

StarCraft II Development History

The decision to split the game into three separate packs was supposedly not motivated by money but in the interest of including more material than would be feasible in a single game. Raynor from StarCraft 2

• Amazon.com lists StarCraft II as available for pre-order for $49.99 with release date TBD
  

• Gamestop lists StarCraft 2 release date as June 2 on a list of games available for pre-order; Blizzard denies comment on date
  

• Blizzard Theme Park Contest announced
  

• StarCraft 2 beta to be released, no date given

• StarCraft 2 available for gameplay at BlizzCon 08
• Blizzard announces that SC2 will now be released as a trilogy with each game featuring a single race and 26-30 related campaigns
• No release date provided yet

• Rob Pardo, Executive Vice President of Blizzard, announces that SC2 is approximately one-third complete at the 2008 Blizzard Worldwide Invitational

• StarCraft 2 available for limited gameplay at BlizzCon 07

• Development on StarCraft 2 begins