Even 128 tracks at CD quality wouldn't come near to saturate the bandwidth of USB2.What surprised me is we aren't going USB 3.0 yet
USB3 isn't necessary in any way to record audio.
As a reminder, CD quality=1.41 kbits/s, USB2=480Mbit/s.
These are theorical rates but they show how much room you got.
The main issue with USB is processor load and USB3 doesn't fix it.