Actually PCI-E 3.0 is still a proposal as there is no complaint hardware. Yes, Intel has incorporated PCI-E 3.0 capability into its Sandybridge E platform, but it has refrained from calling it PCI-E 3;.0 until the responding hardware (read video cards) arrive. There is speculation that the delay in the release of the next generation of video cards is the result of trying to be PCI-E 3.0 compliant.
PCI-E 3.0 like USB 3.0 lacks the hardware to take advantage of the bandwidth. SATA 3.0's bandwidth is used only by SSDs currently. All are future standards, but lack the hardware to fully utilize their advantages.