Well here is what I've got, 4.9 multiplier with a voltage of 1.325 wich is about 10% more than what I would be confortable to use, my temps gots really high, I was able to complete the intel burn test at 1.3 too but it wasn't really that stable, it sometimes BSOD.
I had some results in some test going over 132 G flops but I suspect with those temps I must throttle so I am averaging about 131 G flops.
So, I think that it is possible to go to 5 with aircooler, probly with cryorig r1 ultimate or noctua NH-D15, but my cooler is already compromising my motherboard well enaugh and I'm comfortable at 4.7Ghz with it as an ok OC at 1.235V with temps around 65 C to 70 C with intelburn test.
My motherboard is an asus Z97-A motherboard and my power supply is a really good EVGA 850W supernova gold certified.
My casing is a NZXT phantom410, I like it's airflow and design. Graphic card, gigabite gtx970 g1 and my memory 4x 8 GB ballistix tactical low profile at 2133 - 10-9-10-1t
5GHZ air is possible, intel was right, but, I guess only 5% of the chip can, it is luck of the draw.