If you got the cash, sort yourself an i5 system and hold onto the gpu for now. It will improve all your current games and you can't go wrong with a nice sandybridge setup.
Once the game is released, see how your gpu handles it and if you are happy with the level of detail you can run at, then look at grabbing a new gpu if you need one.
This is pretty much what I did, going from a Athlon x2 5000+ and the difference is huge. I was also running an 5770 at 1680x1050 but have now bought a 2nd one and have them crossfired and am very happy with the result.