Extra time will be spent implementing Early Access feedback
Larian Studios will be pushing back the release of Divinity: Original Sin to later this spring. The title was supposed to be released this week, but instead the studio will be using the extra time to implement feedback received from players in the Steam Early Access and Kickstarter backers.
No exact time frame is given beyond the spring window, but a delay to make a game better is never a bad thing. Of course you can just go ahead and pickup the game today if you really don't want to wait until the official release.