It would be only(mostly) a software update and would not require a new camera, because the USB controller interface currently in place in Kinect can take in data up-to 35MBps. The current utilization is only around roughly 1/2 of it. So there is currently a facility to send more data.
Little more tech data, Kinect does transmit 320×240-pixel in 30 fps, if the device could capture and transfer at 640×480 pixels, then better resolution can detect more movements compared to current level of detection.
Lets wait and watch !