Members of the ID@Xbox program are now able to start using Unity for development on the Xbox One. The news came today during the public preview of Unity Engine 4.3. On top of that developers will be able to publish Unity games for Free of charge on Xbox One.
Unity has explained this announcement saying "We believe this is the best way to empower you to extend these systems to fit your games’ needs while providing a core out of the box experience that will work for many games." It will also come with features that are meant to make the entire process easier for developers such as plugins to help the engine run on the Xbox platform.
There are already a few Unity based games being released in the near future such as Ori and the Blind Forest, Cuphead and Lovers in a Dangerous Spacetime. The Xbox One will receive the 4.3 version and will be upgraded to the 5.0 completely skipping the 4.5 version.