If you have a good enough processor with a good enough encoder, you can do a lot with USB2.0. For those wondering, you can try watching 1080p+ streams, if the streamer has a good enough PC, they can have bit rate as little as 3000kbps and still have a very watchable quality. [There are pros who stream at 12000kbps, and I do know the image is insanely impressive, but those are few and far between]
And since USB 2.0 is rated at 480Mbps, it has potential to do a lot more than it is doing now.
Unfortunately, The biggest issue with USB 2.0 is that it has so much overhead that it is slower than Firewire 400 in raw bandwidth and would be closer to about 260-300megabit/sec(that is 33-38megabytes/sec) on most hardware.
I mean it has NO issue watching lets say bluray at 1080p(compressed video), but the 480megabits/sec is pure marketing just like wireless network cards with collision avoidance taking about half the bandwidth.
If they update their devices to support USB 3.1 then they shouldn't have an issue since it supports twice the speed as USB 3.0
The issue is not so much the bandwidth but rather the protocols that were in place when USB was first developed are still in place for even USB 3.0.
First off is the encoding scheme (8b/10b) which means a automatic 20% drop in data rates. It was the same as PCIe 2.0/2.1 and 3.0 changed to 128b/130b to drop the loss greatly.
There are others and while they are implementing others that help USB perform better, its original idea did not allow for the massive amount of data to be transferred. This could work well as a single use of USB but when you add more devices using USB, it will slow it down considerable.
This is what eSATA and Thunderbolt are being designed for. They are designed as single link systems that have their own channel per port while USB is a single controller working for multiple ports.
Of course USB is much cheaper as it has been around long enough to saturate the market and just switching is hard unless you take the approach Seagate has with their GoFLex style eHDDs which makes it easy to move to the next or better interface.
They say they do 4k but they don't mention bitrate or frame rate. Makes me wonder how good the quality is. Not that I don't mind using a single cable for everything but can I play a 4k 3D blu ray over display link? HDMI can't do this yet and that's what it was designed for.