The SDK will also include some maps from Counter-Strike 1.6 that did not make the transfer to Counter-Strike: Source. According to Valve boss Gabe Newell on the Seven Day Cooldown podcast, both CS 1.6 and CS: Source have been integrated into Global Offensive "unless the beta testers are blowing smoke up our ass."
Counter-Strike: Global Offensive is due to be released sometime this Summer on PC, Xbox 360 and PlayStation 3.