Oh dear :(
This is going to end badly.
The thing about USB1/USB2 is that it all runs down the same cables with standardised connectors.
USB3 with its seperate transmit/receive busses means its NOT backward compatible with USB2, they are only claiming it is because they've added extra pins and just left USB2 in there alongside it.
Now thats all very nice on paper, but you can you really see manufacturers with names like "Unbrand-o-tron" bothering with that?
I see a future where you will have USB2 cables, USB3 cables that do USB2 and USB3 cables that only do USB3. I can see the same applying to some devices and host controllers too in order to trim a few cents off the bottom line.
I'm not saying this bus is bad, I'm just saying that trying to market it by abusing the name 'USB' is going to cause trouble. I think this bus would work a hell of a lot better if it simply had a different name, aslong as its called USB people will expect a level of compatibility that real world economics will not allow. Great, if you are selling kit and cables to customers who don't know the difference, once you've sold them the camera that only supports USB3 you get to sell them a host controller and a new set of cables too!
And then there is the question of where does it end?
I mean, if this multi-bus system was taken to extremes we'd end up with a six foot wide connector that has a serial, parallel, composite video, rgb, dvi, ide, sata, ps2.....