An new filing with the FCC by Sony suggests that the console make has some sort of wireless adapter planned for the PlayStation 4.
The certification (via DualShockers) has led to a variety of speculation based on the product code CUH-ZWA1U. Apparently CUH signifies PlayStation 4, while the Z usually references controllers. A likely possibility is a dongle for the DualShock 4 that allows it to be used wirelessly on PCs. There are plenty of other scenarios, ranging from Bluetooth headsets to Sony's own proprietary headsets.
Since the information will be confidential until 2017, we'll have to wait and see what Sony has in mind. It is fun to speculate, though.