We found proof that you can use a PlayStation 4 controller on your PlayStation 3. If you can recall, this is the same guy who unboxed the PS4 debug console. We featured his video last week to let readers get a glimpse of the console.
From the video, we learn that the Dualshock 4 can be used if it is connected via a USB cable. Wireless does not seem to work between the new controller and the current generation console.
It was not clear if he could use the touchpad, but I highly doubt you could since it is most likely an exclusive PS4 feature. Otherwise, it seems to work fine but don't expect to walk far distances with the controller.
The PS4 will be out on November 15th.