Yeah you have a solid 5-6 months before you need to pull the trigger. Nvidia and AMD will both have some great offerings on both the 600 and possibly 700 series and the 8000 series, respectively. I purchased a 670 after trying a 680 and imo it's definately the same card, I tried several resolutions on Battlefield 3 all on maximum settings and the 670 was identical to the 680 performance wise. I am an nvidia fan, I tried the 7970 but returned it several days later, not because it couldn't perform, but rather the card is just so long that it was conflicting with other components in a HAF 932A case (which is a huge case). Other than the fact that the card was huge, it was still a great performer none the less. Each card has benefits, and each card has flaws. AMD still has the advantage of running 3 monitors off a single card, to some people that is just worth it's weight in gold.
But like everyone has said in this post, they will both have some great offerings in the not so distant future, I hope you find what you are looking for.
Case closed.