Sata series 1 is 150MB/s, series 2 is 300MB/s series 3 is 600MB/s
The potential of usb 3.0 (which most computers don't have today) and adding it on would sacrifice a video card port to deal with the required througput, unless they found a way to utilize extra sata ports to get the bandwdith & THROUGHPUT necessary. This won't become a gotta have until flash drives are affordable for the masses and can replace hard drives.. in the multi-terabyte range for under $200. At some point, main hard drives will be ultra fast flash and storage (server) drives will be behemoth 8, 10, 15, 20 TB'ers. For now, you're not going to need more than 1tb for your system drive for some time..