Intel is expected to launch their Skylake processors in just a couple of weeks at Gamescom and it looks like there are already a few samples in the wild. If these screenshots are believed to be real it looks like whoever is testing this chip was able to get it up to 5.2 GHz on air cooling!
This image comes from HKEPC who look to have a chip on hand for testing. They have upped the multiplier to 52X giving the chip a speed of 5.2 GHz, that is a 1.2 GHz overclock over the stock 4.0 GHz of the chip! Even more impressive is that this overclock was done with only applying 1.35V to the CPU and the system is running on air cooling!