While those that have tried using the PlayStation 4 DualShock 4 controller with their PlayStation 3 by connecting it with a cable will tell you that it works. While it does not support the motion and rumble, it still works with most games.
Sony has quietly enabled wireless support for the PS4 DualShock on the PS3 with the latest firmware update. Once paired with the PS3, the system sees it as a generic controller. This does mean that not every game will work, but it still can be added via the PS3’s Bluetooth device management menu.
Some players feel that the PS4 DualShock simply has a better feel than the PS3 DualShock. Now with the wireless support, you can really get a chance to test it out if you are willing to give up the motion and rumble abilities of the controller.
Read more here.