I had a 4890 which should be just a tiny bit better than your 5850, but it's Dx10 so it doesn't play Dx11 only games. I can say it still played mostly everything I threw at it, but it couldn't handle Rome 2, for example, even on my new i5 4670k and Z87 motherboard. It wasn't the first game I had found to be unplayable either, hence my upgrade.
I don't image you'll be keeping your 5850 for more than a year, unless you really don't fancy any of the new AAA games that'll come out this year. Or maybe stardock's new space simulator? I hear it's gonna wreak havoc on old cards.
