If I were you I would wait, Sandy is supposed to bring better power effiency, better performance, and cooler chips. Which should replace the chips in the G73 leaving it at the same price, but with better performance. Theres also the chance of better gpu's also.
My guess would be that since its launching in Jan. we should see the chips implemented by feb. or march since asus is a pretty fast at adapting new parts.
I've been waitng a year for this lappy. My dream machine is the G73 with sandybridge + 580m + optimus = BA gaming laptop, with 3-4 hour hours of regular use, that will last me through college and it appears that the next refresh of the G73 should bring it.
Wait for Sandy Bridge? - keep in mind that initial offerings will be at a high price! Then what would be the decision? Wait for the price to drop?
The answer to your question is "If you need a laptop now, buy it now" - there will be some good deals during the holidays season.
I dont believe prices will be high, when the first i7 mobiles came out and replaced the core 2 duos and quads the prices on high end laptops remained the same. My guess is that the same will happen this time around. Just an assumpption though