Intel's Sandy Bridge released in January of '11, and that is still very much a good gaming Cpu. If you paired that with an Nvidia 970 or higher, you'd be gaming at max settings for 1080p resolution, and that Cpu is almost 5 years old now.
So I'd expect that much newer Cpu to last 4+ years easy. Like others have said though, your most important piece of hardware is going to be the video card for games. However, the 4590 should be strong enough to feed enough information to the newest graphics card in 4 years, so your still good to go.