The USB Type-C port is a curious beast. It is, in fact several connectors in one:
- A high speed data path
- Power delivery
- A USB 2.0 port
Now, the high speed data path can be used for really speedy USB, 10 GBit/s "Superspeed+" mode. Then you can connect this to a speedier version of the plain old USB hub and have as many USB 1.1/2.0/3.0/3.1 devices connect to the hub as you wish.
Or it can be used in an alternate mode. This can be a lot of things, currently DisplayPort, HDMI, MHL is supported but the potential is there for Ethernet and even PCI Express and whatnot. However, let me emphasize again: if you do this then your superspeed+ USB is not there. You can still use the power delivery lanes and the USB 2.0 port. The latter is a usual High Speed USB 2.0 port, goes into a USB for USB 2.0 devices.
There will be a lot of confusion because the charging only USB C connector on the (some video)/USB2/(USB C charging port) adapters is visually not distinguishable from the versatile port on the machine. Theoretically you could even build an adapter which has all sorts of ports on it and a button that switches which one is active.
Even more confusion will arise when accessory manufacturers will create a SuperSpeed+ "docking station" that has a kind of DisplayLink chip in it. Remember, DisplayLink is the technology behind USB-to-DVI adapter but this time the bandwidth is quite there to do uncompressed video over USB 3.1 -- it's less than half of the available bandwidth. With compression you can even do a dual display adapter! At least for 1080p60 or 4k30 you can. Perhaps it'll even be possible to drive a 4k60 monitor this way. There's a possibility that such a docking station will feature one or more of the familiar blue USB 3.0 ports or even USB-C ports just for fun and confusion. Because these USB-C ports are now locked to USB mode and can't be used with native display adapters.
Other docking stations, however, will switch the USB-C connector to DisplayPort, add an MST (MultiStreamTransfer) hub and drive three displays natively and happily (as long as they are only 1080p). These ports can have USB 2.0 ports but not 3.0/3.1.
Basically there will be a tonne of scenarios where users can plug in something into an USB-C port and it simply won't work. At all. Or where you plug in a monitor, expect it Just Work and faced with needing to download drivers.