For gaming, you without question do not need a new cpu, for some time. Some big new stuff next year, potentially hugely hugely faster, but even then it will likely take games and other stuff a while to require them. Quads, were total overkill when they came out and are really just starting to come into their own, games this year will probably show a edge on quite a few things on quads over dual cores..... maybe.
Quad cores are just going to last a lot of people a lot of time, really any upgrade you could get now or this year will be a sideways move, the Q6600 being a particularly awesome value chip.
Next year new stuff, not sure what price AMD's new architecture will aim for, but the good news is probably that it will be a good while after it appears(and intels next gen stuff) till you might need it for games so if you haven't got the upgrade bug, getting something next gen a few months after launch will probably net you a pretty huge boost for decent value.