Re: GTX 580's, or wait for Kepler?
I play games all the time that I would consider unacceptable to play on a single 580 with the settings I normally use. And yes, that's at 1080p.
And as for waiting for Kepler, people have been saying that for nearly a year now. Unless you know the exact date it is being released there is no need to wait. It could be 3 months or it could be 6. If something goes wrong with production it could be another year. On top of that it's quite possible that the top end Kepler card could be slower than 580's in SLI. So you wait all that time and end up with a slower solution.
Buy when you are ready to buy, don't wait around for what's coming because you could do that for the rest of your life.