This is the second time Harmonix has made such an announcement this year. Last month, the developer revealed that Rock Band 3 will receive no more DLC after April 2. The Rock Band franchise as a whole has had weekly DLC since the original game debuted in 2007.
That raises the question: Just what is studio working on now? Dance Central has consistently been one of the best-received products for Microsoft's Kinect, so it wouldn't be surprising to see a new Dance Central debut on the next Xbox, which is believed to have a more advanced Kinect sensor. The PS4 Eye is capable of motion-track as well, so a multiplatform title is also possible. Or who knows, maybe we'll see something entirely new.