My current setup is over 4.5 years old now and still runs very strong. I game often, even modern games (like BF3). My goal is to get a new GPU that will last me another 4.5 years. I think I'll end up stretching it to the GTX 580. I'm not ruling out ATI yet either, but my Wife's PC has a GTX 570 and it rocks.
Although her PC also has a Intel quad-core i7.
If I upgrade the CPU this year, then I'll probably get a new motherboard, etc just to complete the upgrade (but I lack in knowledge about socket size these days, so not sure if a new motherboard would really be needed).
Thank you all for the feedback so far.