Pretty much for 99.999% of the folks. Running a single GPU (ANY) on PCIe 2.0 x16 vs PCIe 3.0 x16 on a HD (1920x1080) makes ZERO difference. Now once 4K monitors are the 'norm' and you're looking still at multiple GPU's then sure -- long way off.
One more thing, in order to have PCIe 3.0 everything MUST be PCIe 3.0 compliant:
1. GPU: GTX 600 series or HD 7000 series
2. CPU: Ivy Bridge ; the i5-2500K is PCIe 2.0
3. MOBO: GEN3 or newer e.g. Z77's
If any of the (3) three is PCIe 2.0 then you get PCIe 2.0 link speed.