Using the DualShock 4 to play your Steam-based games will no longer be a pipedream as Valve has announced they will be expanding the Steam Controller configurability options to support the DualShock 4 is a future update.
Speaking at the Steam Dev Days event, Valve’s Jeff Bellinghausen mentions that the DualShock 4 has numerous overlapping functionality with the Steam controller. For example, both controllers come with a gyro and a touchpad. When the update goes live, those with a DualShock 4 will be able to connect the controller directly to the PC and use it without requiring any emulators to do so.
Valve did not mention when the update will be available, but the company did hint that it will also be supporting other controllers. What those other controllers are, Valve did not specify.
Source: Gamasutra