Valve will soon make it possible to use the DualShock 4 controller for the PS4 on the PC in combination with Steam. This will be done via the same api as for the Steam Controller. In addition, Samsung TVs will receive support for Steam Link streaming from the PC.
The DualShock 4 controller is just the first controller that will work with Steam on PC via the Steam Controller API, with more to come. The reason the PS4 controller comes first is the overlapping functionality with the Steam Controller, such as the presence of a gyroscope and touchpad. Valve announced this during the Steam Dev Days. Gamasutra has a transcript of the announcements.
Valve also announced that it is expected to reach one million Steam Controllers sold by early 2017. Sales will be expanded to include Eastern Europe, Southeast Asia and South America. In June, the counter stood at half a million. Every day, an average of 27,000 gamers play with a Steam Controller on the Valve game platform and 1.2 million configurations for the controller have now been shared.
In addition, during the Steam Dev Days, Valve announced that Samsung TVs will receive support for Steam Link as standard. That writes Polygon. The Steam Link box costs $40 and allows streaming PC games to the TV. It is not yet known which TVs from Samsung will receive support and what the support of controllers is like.