I think people are understating the importance of PCI-E revisions. Correct me if I am wrong, but I believe the southbridge to CPU lanes use PCI-E lanes (which is why a lot of time you see having a large amount of SATA ports limits the PCI-E slot bandwidth, and maximum slot bandwidth requires fewer SATA ports or the inclusion of a 3rd party SATA controller to handle the extra load.)
In that case, an upgrade to PCI-E bandwidth will mean more headroom for the slots, sure, but also more bandwidth for the southbridge too and less bottlenecks or connectivity sacrifices. Also, don't forget that the next video card generation will be a jump to 28nm, which people are speculating to have a very nice performance jump. We will be putting those PCI-E slots to work, make no mistake. Maybe single cards will get by with no penalty, but I think crossfire/SLI users will be wanting either those PCI-E 3.0 x8/x8 slots or PCIE 2.0 x16/x16 slots. Anything less might fall short.