It is a timed exclusive. First release on the Xbox One, then the Xbox 360.
Hopefully they'll fix the issues people had with the original game. The main issues were no story and poor controls. I think Kinect on the Xbox One will fix the controls issue, not sure about the Xbox 360 version. Maybe why they're coming out on 360 later. If Xbox One console sales and Fighter Within reviews/sales on the console are solid, then I think they may come out with the 360 version. If not, they may drop it all together.