I think you will have a long wait for that price! i doubt netbooks will get USB 3.0 until laptops get it mainstream! Desktop motherboards with USB 3.0 are in that price range, so i would say at least 12 months for that price bracket netbook.
Just remember with USB 3.0 that if you plug a USB 2.0 device (basically all deviced out there) into the same hub you will only get USB 2.0 speed. Despite the chipsets supporting numerous hubs, usually all the ports on a motherboard are run from the sam hub! They do this because its cheaper to do so, and people don't notice... This means that if you are using multiple high bandwidth devices through the back USB ports, your speed will suffer. Front ports etc are connected to a different hub via the connectors on the motherboard. I think this is why intel for example hasn't really jumped on to USB 3.0, since for most people it will be running at USB 2.0 anyway due to USB 2.0 devices being connected. Not to mention that even if it was running at USB 3.0 speed, people may use non-USB 3.0 cables (yes, they are different as they allow bidirectional support). The USB 3.0 ports work at USB 3.0, because they are completely separate to the inbuilt ports provided by the chipset, and provided by a third party vendor (NEC etc). As long as you don't plug a USB 2.0 device into these ports as well as a USB 3.0 device, and you used a USB 3.0 cable, you will get USB 3.0 speeds. I never understood why they made USB uni-directional, meaning it has to cycle between sending and receiving data (because even if sending or receiving, the target device needs to signal). This cycling causes a considerable slowdown which is why you will never see 60MB/s transfers (which was originally claimed, aka 480 MBPS) to external drives through USB. Also ensure you haven't got EHCI handoff (or whatever its called, I can't check at the moment) enabled in the bios, as that may make USB 2.0 devices run at USB 1.1 speeds, and result in that 'this device may perform faster...?' notification...