They want to "incorporate them in the story," the game world and mechanics so they need more time. They chose a late February date instead of cancelling a feature or goal.
Larian knows this might upset some who wanted their RPG slice this year but Alpha access backers will get a "rough and rugged" version this November.
Beta backers should receive their access in early January. "We are very determined to implement all the extra features gained through stretch goals the way they should be implemented, which essentially means that we want to incorporate them in the story, the world and the gameplay mechanics," posted Larian Studios.
"This is taking us more time than we originally thought, and so, rather than cancelling a feature or a goal, we decided to move the release of Divinity: Original Sin from this fall (as originally announced) to this winter," they said. "We realize this may be disappointing for some people who had hoped the game would still come out this year, but really, we think you'll have a much better RPG experience when everything we wanted to put in, is actually going to be in."
The new release for Divinity: Original Sin is February 28th, 2014.