The USB Implementers Forum has announced the USB Power Delivery 2.0 specification that will deliver power for multiple devices, including monitors, over one cable. The USB Type-C connector can handle up to 100 watts, which is more than enough for a display, including DisplayPort.
What this means is USB Type-C can carry DisplayPort 1.3 HBR3 signals over the wire, which means it can drive a 4k display at 60Hz, and still have enough room for two lanes of USB Superspeed+ (USB 3.1) available for any devices plugged into the display.
It also means laptops with DisplayPort can send their signal out to a display, and not just USB Type-C. It will also support DVI, HDMI or VGAs for those who still use them.
The USB Type-C spec, which will utilize the USB Power Delivery 2.0, is notable because it has identical connectors on both ends, instead of the square plug on one end of a USB 2.0 and the wider, flat one on the other end. It will also transfer data at a rate of 8.1Gbits in both directions, per lane, and will eventually be boosted to 10Gbits.
Another thing that separates Type-C from previous generations of USB is that users can actually control the use of the four signal lanes. You can set two to a 4K display, leaving two other lanes free, or you can use just one lane for a lower resolution monitor.
This likely means monitors can be used as USB hubs for a PC and a single Type-C cable connects to the PC. How this will work with discrete video cards is not clear, and that's one thing I want to see clarified.
Now it falls to vendors to adopt Type-C, and we're still getting USB 2.0 devices on the market. Apple is rumored to be planning a MacBook with the Type-C port for 2015, and if this port is all it's cracked up to be, expect it on motherboards by next year as well.