I would definetly wait a die shrink happens soon and not only this but new architecture is coming to. Fermi was used in the GTX 4xx series too also between GTX 4xx series and GTX 5xx series was no die shrink.
The GTX 6xx series is worth waiting for just 3-4 months and you get 28 nm Kepler and not 40 nm Fermi like GTX 4xx and 5xx series. Which means a lot more power for the same price and definetly more future proof.
I would endure the new games with lower settings for the next months to get a bigger jump later







