I expect that anyone who really needs the extra
speed of USB 3.0 in the near future will get it via PCI-E plug in card. I also suspect few need it it at the moment.
Personally, I think USB is the way of the future and expect to see some internal USB 3.0 hard drives and RAM expansion units in the near future too. I recently saw a new desktop computer that had six internal SATA drive connectors, two IDE connectors (for optical drives only - according to the paperwork), a built in graphic processor with a graphics port, built in sound processor with plugs for a 6+1 system, two PCI-E slots, and eighteen USB ports.
Eighteen of the suckers, it astounded me, so I started checking off what USB devices I could find around my house used by my son and I - keyboard, mouse, scanner, printer, external hard drive, web cam, digital camera, cell phone data transfer cable, link to notebook cable, USB / modem link, USB / network cable, USB TV wand, data cable for e-book reader, game pad, media storage unit (my son's not sure exactly what it does, but that's on the case), data link to UPS, and three other USB cables for devices I can't find - sheet, everything connects by USB now, except the graphics and sound, but give them time.