Soon the USb3 audiocard will be the majority on the market.
Hey Freddie,
Don't disagree with the sentiment... but I wouldn't expect this "soon".

I've yet to see a single official announcement of a (pro-level) USB3 audio interface.
Unless you're using a Z77 chipset motherboard, your USB3 ports are provided via 3rd-party add-on controller. Many current USB2 audio interfaces have slight to major compatibility issues with these controllers.
ie: The RME units "work" when connected to one of these USB3 controllers... but you can't run as heavy a load (glitch-free) at the smallest ASIO buffer sizes. The FastTrack Ultra 8R won't work at all...
Liken the situation to "rogue" chipset Firewire controllers.
I think this is the reason why audio interface manufacturers have been dragging their heels on USB3 units.
It would present a tech-support nightmare...