Hold onto it for a little while. You'll eventually want to go newer CPU, more cores, etc. But if you are happy with the performance and it's not maxing out the CPU, then start with it. If you went new platform, you would need new motherboard, CPU, and ram also. Ram is high right now as well.
You could always see if you can score an i7 4770k or 4790k on a good deal though, then overclock that and be set for 2-3 years.