7950 cost 450$ at newegg now.
GTX6** will be released in April 2012. (http://lenzfire.com
) but nobody can guarantee it.
So there will be no "reasonable price" for 7950 next two month.
Hardcore overclocked 7950 will do 550Mhash/s or ~0,35BTC/day or 10btc/month or ~60$/month aaand fiiiiinally 120$ total (until GTX6** release).
120$ is ~30% from 7950 price.
So if you think that 7950 will be cheaper more than 30% after GTX6** release - keep your cash at home. And if you think that GTX6** will not be released in april, or 7950 will not lower it's price for 30%+ it's time to upgrade!