Why don't they just say it. They pulled them for Dance Central 4, and because the new Kinect uses way more motion cap points, they stopped bothering with creating new dances for the Old Kinect. They are most likely busy going back through the Dance Central library and converting all the dances to new Kinect/ Dance Central 4 standards.
Source:
http://www.gameinformer.com/b/news/archive/2013/03/08/dance-central-3-dlc-ends-in-march.aspx