While nothing yet saturates the USB 3.0 there are plenty of items that saturate the USB 2.0 bus so there is a gain to be had. I have a couple devices that will push 880 Mb/sec (110 MB/sec.) Which coulnd't get anywhere near that plugged into a USB 2.0 port.
Here is reality, first you should have read my pinned FAQ post at the very top of this section of the forum. This very topic is covered in there, thanks for being lazy. Second the SOC in this product has only a USB 2.0 bus for an external bus so all bandwidth is shared by that bus, aside from the SD card. The next problem is that there just isn't enough processing horse power to drive good speeds out of USB 3.0 devices. Lastly, aside from the cost of the USB 3.0 IC the USB 3.0 specifacation requires 4 more traces on the PCB (more complex = more expensive) and more expensive jacks.
There are no ARM SOCs at this point that have native USB 3.0 support, however there is at least one that has an PCIe out on the chip and that could be paired to a USB 3.0 host chip. However this chip has no GPU, and since I own one I can tell you that even though it has native PCIe and SATA getting more than 280 Mb/sec (35 MB/sec) is impossible even when the device is formatted ext4. It is the Marvell Kirkwood and even though it is clocked at 800 Mhz it chokes at speeds much lower than the max of a 2.0 port. Though I have never tested the SATA port only the USB 3.0 ports.