It's hard to imagine that Dance Central was in development before Kinect was even announced, but Harmonix is now saying that the game was slated to have its own peripheral before Project Natal hit the scene.
In a speech at GDC Europe, lead designer of Dance Central, Dean Tate discussed the development of the title. He said that the game was in development for 17 months, with the first five of those devoted to developing prototypes for the dancing system.
Some of those were based on button presses and accelerometer motion controls, while others relied on their own hardware. Development changed once Kinect was announced, but Tate said that if it had not been announced Harmonix would have continued with development using their own hardware.
Tate went on to discuss several other topics including the difficulty of developing an effective prototype and the fact that Dance Central 1 only had "20%" of the features they wanted to implement (many of which will reportedly be appearing in Dance Central 2, such as simultaneous multiplayer.)
The full GDC Europe panel rundown is over at GameSpot.