The next generation of graphics cards will be based on smaller manufacturing process. from 40nm to something in the 20's.
That will make the chips cheaper to produce, run cooler, run faster, generate less heat, and use less power.
All good things.
In the past ati and nvidia have tried to catch the Christmas buying season.
If possible, I would expect that time frame.
Otherwise, look to spring 2012.
Top end chips will command a premium price, so I would expect them first.
Pricing will, as always, be what the market will bear.
You will see price reductions on lower end cards to clear out inventory, making way for cards that are cheaper to produce.