Hello.
At the moment there is no upgrade to justify the gaming upgrade from i5 2500K to any CPU.
Stay with this, games just started to make the 4core a mainstream so you will be fine with this great 4core with one of the highest per core performance.
Also when you feel that the performance is not enough after 2 years, just oc it to 4,5Ghz which for a 2500K is like nothing...