Ok one day after the PS4 announcement they confirmed a PS4 release in an official press release and they were ver happy and hyped about it. Now a few days after they Xbox one reveal they still did not confirm this. All they said was:
"We will shed more light on [The Witcher 3] during E3," CD Projekt Red managing director Adam Badowski told GameSpot. "I'm sorry but I can't give you any details right now."
Given how CDRED is a very very consumer and anti DRM company I somehow think they will not release The Witcher 3 on the next XBOX. They also were really happy how Sony supports them so chances are very high that you will not see a XBOX one release of this game.