Don't get too excited just yet, but PCIe 4.0 is coming. PCI-SIG, the body that governs the standard, has announced the next evolution of the interface, which should start popping up in servers, desktops, laptops and even tablets around 2015. Sadly, details are pretty slim on the slot -- final specs aren't expected to be announced before 2014. All we know is that PCIe 4.0 will be able to perform 16 gigatransfers per second (GT/s), which tells us only slightly more than jack squat. It simply means that a PCIe 4.0 card will be capable of transferring 16 billion discrete chunks of data per second, twice that of PCIe 3.0. What that doesn't tell us though, is the size of those chunks. If they're the same size, 4.0 will provide double the current bit rate of 1 GB/s per-lane. If, for some reason, the channel width were halved there would be no speed increase -- but we seriously doubt that's the case. So, will we be looking at 32 GB/s PCIe 4.0 x16 GPUs in a few years? That is a definite maybe.

http://www.engadget.com/2011/11/30/pcie-4-0-inches-towards-reality-hits-16-gigatransfers-per-secon/

So whats the point if we haven't even been able to fully utilise PCIe Gen 3?

m0ar bandwidth!!!11!!1!oneBut in all seriousness, until at least 2015 it won't be available. Just planning ahead

Yeah, i guess. Might be time for a whole new slot after Gen 4.