I skipped X99 and stayed with my X79 setup as the CPU performance increase wasn't great enough to warrant the expenditure. Almost £1000 to get CPU, Motherboard and DDR4 Memory for a 10-15% increase in single threaded performance (3930K -> 5930K). Just didn't seem worth it.
I think I'd be on board if they lower the price of the 8 core (which I doubt they will) or the IPC gain is substantial like 25-30% over Sandy Bridge-E which is what my 3930K is.
Would be nice to get some of the newer features as-well like the M.2 slot for a 960 Pro etc
Despite being interested in seeing what Skylake-X will do, I don't think I'll change my setup until Intel brings mainstream 6-core to the market that boost to 4.5GHz + out of the box on all cores. And make them affordable ha ha; any enthusiast platform, like X299 is well over my budget.