I can confidently say that I'm not going to be getting rid of my X4 965 on an MSI 790FX-GD70 for a long time. Does everything I want it to right now, and I'll probably just drop in an HD 6970 or similar when my 5770 stops being able to handle the games I want it to run.
But no. It wouldn't be worth it. Invest your money somewhere else until your Phenom actually gets outdated and can't do what you want it to.