Most benchmarks I see show the chips at STOCK speed for gaming benchmarks, and in that case they are still GPU limited most of the time. Now add 1 ghz to the chip like you have and think about the benchmarks then.... even if the Skylake is 25% faster in a few specific games... its still not even close to worth it. Maybe if you have SLI 980 TI's and run 4k, which in that case you have money to burn anyway. If you're gaming on a 670 and considering upgrading just now, the 2500k is not holding you back in anything.
Platform upgrade, give me a break. Is the system going to do anything noticeably better because of the platform? 100 SATA ports, support for a USB version no devices use yet, and $12 a year less electricity. Sweet!
I don't have a problem with Skylake, its more of a testament to how good SB was and how stagnant gaming graphics and performance have been over the years. But you won't even notice a CPU upgrade. Get a 980.