I am always cautious to say something can't be done, especially on this forum. But,
The arduino is nowhere near the appropriate platform to process or even communicate with Kinect. Besides the speed issue you identify, the limited memory size is an even greater problem.
Get yourself a low cost embedded linux board with HIGH speed USB 2.0 ports, 32 bit data paths, DMA, a few meg of spare ram, and 100s of megahertz.