This was why I bought a i5 to start with and dropped my AMD x6.
Most games are still going to run as good on a dual core, however newer games are going to take advantage of quad cores and be faster on them.
I may wait to see some pricing options once Bulldozer is released before I replace my i5-2500k setup.
Another thing that weighs on my mind is how long before 6 or 8 cores becomes to new quad core... In that most games just just as good on a quad, but newer games start to love x6 and x8 chips.
Edit: It will happen, there is no question... The question is will it happen before Haswell, or another chip design when I'm ready to upgrade from my 2011 purchase.