Gpu's are needing more and more watts at the years go by. So it is safe to get a bigger better psu then want to upgrade a gpu and not have the means to.
I disagree. I think they are getting more power efficient, unless you mean Nvidia cards. Only the extrememly high end cards pull lots of power. In fact you don't need a 850w psu unless your running SLI GTX570's.
Oh and cpu's are getting more efficient as well. All quad cpu's used to be 125-140w. Now they are down to 95w on the quads and run much faster.