I highly doubt that there will not be any 16x/16x boards, otherwise i5 could not compete with Phenom II in multi GPU performance now that 16x/16x is actually beneficial.
I know the P55 chipset will come out first. There will be an enthusiast chipset, the x57(or P57) which I have not found much detail on yet. You would think THIS would include 16x/16x support. Look at the P45 now? it only has 8x/8x support. It is not ment to be for the enthusiast. Besides a pci-e 8x 2.0 will run most any single gpu card just fine.