No AMD boards currently support PCI-E 3.0.
If a GPU needed PCI-E 3.0 to get the full performance, you wouldn't be looking at an AMD CPU anyway.
PCI-E 3.0 isn't needed at the moment.
As to when they'll be available? I'm not sure, 1090FX is touted to launch with Steamroller to my understanding, so if it came with Vishera boards, unless they changed the 990FX chipset, it wouldn't be native.