I dont see USB taking over ethernet for networking anytime soon for 2 big reasons:
1)Ethernet and USB are so different that it would cost waaay to much to roll out USB in place of Ethernet.
2)Current USB standards say that a USB device cant be more than 5 metres away. Ethernet (with Cat5 Cable) can run for 100m.
Also, IBMan, Cat6 is a standard for Ethernet cables, not for actual transmission speed.