That might just be a dedicated port for Kinect, but if there is an adapter like @iroboto said, then it's likely a normal USB port but without the additional power requirements for Kinect. The Adapter will likely be similar to the X360 Kinect adapter where it plugged into the USB port and then the wall socket to provide the additional power required for Kinect.
Or maybe there will be a mini-kinect that requires less power since the IR Blaster is now part of the base console?
The Kinect adapter is also going to free as well, but I think you need to request it via MS.