It all depends on you, but in my opinion, I think its better to wait and make sure all TRUE NEXT generation parts are out to make the next build worth while. If you already have a sufficient and "once future" proffed system like I do, it is better to wait just a few more months for the next gen parts like cheaper yet better SSDs, X58 boards w USB3.0, second gen 1333 core i7's, GTX300's Ati 4850's,4870x2's, Blu-Ray drives that are cheaper, cheaper DDR3, and Win7 sp1 at the very least for a true next gen system.
If you have even more patience AND money, you can wait for the Hexacore Chips. So if you have some extra cash to spend just wait or buy a GPU but since your system is almost maxed out and is still good(future proofed), wait and build for something that will make you use your PC for at least 3-5years. Thus one last thing, wait for USB3.0 and WIN7sp2.