Most USB 3.0 devices will simply be USB 2.0 devices that are "tested" or "certified" or "labeled" to be compatible. We went through this on the conversion from 1.1 to 2.0. Marketing people will say anything to get you to buy them.
Also USB 3 devices are supposed to be backwards compatible to USB 2.0 signaling. This will make it hard to determine if you are getting the performance of USB 3.0 that you will be charged for.
Even today, many devices are not capable of running at the spec for USB 2.0.
Some day we will see true USB 3.0 capable devices and devices that use/can take advantage of that bandwidth. At that point, you will need either a PCIe adapter or a new motherboard to make use of the speed.