Definately wait for the G71 in March at least. Its going to make the 7800GT/GTX look like the FX series did to the 6800 series. Basically, now is not a good time to buy a 7800 series card because the G71 series is going to double performance.
I would imagine the G71 will be recommended for Elder Scrolls Oblivion which is comming out at the exact same time. I say it will also be minimum for playing UT2007 on 1280x1024.
Makes me wonder if they delayed Oblivion because they didn't like the results they were getting on current cards.
The G80 is the one I am waiting for, and since UE3 will be the standard for a while, my G80-based card should last me a while.