Can I use a printer requiring a USB 2 port in my new computer that only has USB 3 ports?
Yes, and you can use USB 1 devices on USB 3 ports, as well. This is much like USB 1 devices with USB 2 ports. Unless USB 4 changes greatly, which would leave many devices incompatible, I don't think one would have to worry about incompatibility issues for a while.
quite right Dalsan, in this case (USB 4 changes greatly) they will make adapters, but no one would like to use adapters;):):)
As Bruce says, USB 3 ports are backwards compatible. You can plug your USB 2 devices into the PC and use them without any trouble, albeit at USB 2 speeds.
Yes, you can. USB 3 ports can drive devices requiring previous versions. The reverse is not true. USB 3 devices cannot be driven by previous USB port versions.