USB 3.0/eSATA begs to differ. And it wouldn't be always on.
too bad everything Nintendo has told us so far says "4 USB 2.0 ports"
usb 2.0 reads at 35MB/s if i've done my homework whereas BD at 8x hits 36 MB/s, further research suggests a 'theoretical' 12x at 54... so maybe usb 2.0 is all that's really going to be necessary