I would search your favorite manufacturer's websites, such as asus and gigabyte. I've emailed them before about upcoming releases, but they often won't give out info. When new stuff is in the pipeline, they'll start releasing press info on their webpage. The other option is to write amd or nvidia and see if their new chipsets will have sli or crossfire.
It's true that PCIe 3.0 is not needed at this point because you can't even saturate PCIe 2.0 X16/X16 in SLI/Crossfire. PCIe 3.0 is a marketing ploy to try to get you to buy a specific brand of mobo. There is no performance advantage to it at this time nor likely in the next few years.
The main use for PCIe 3.0 is not bandwidth for graphics, but the for bandwidth required when the GPU is used as a computing workhorse; using it so can easily saturate a PCIe 3.0 bus just for communications between the GPU and CPU.