Why are people expecting any IPC increase? The mind boggles, it might gain some performance in specific tasks, but the quoted single thread increase is clearly just from a faster boost/turbo clock. Put the 8700K up against the 7700K at the same frequency and it'll be margin of error differences.
The 8700K is a 6 core 7700K, so I have no idea why anyone is getting excited, it'll be $350 twice the price of the R5 1600, and a waste of money if you are gaming only, the 8600K will need to be £199 or less to get the best bang for buck, but I'm sure it will take the performance crown for gaming, certainly it will make the 7700K and 8700K lot massively over priced.