My 6700K is perfectly stable at 4.6Ghz. It overclocks fine. But there is no reason to upgrade Haswell to Skylake. You will see a big 5-7% performance increase clock for clock and that's only in certain situations.. Certainly not worth spending money on a CPU, motherboard and new RAM for the 1 or 2 FPS you would get. If you want better gaming performance you need a better graphics card.
Your 4770K should do 4.1Ghz -4.2Ghz on stock voltage with no problems.