Well, I haven't heard much about a 9800GTX. No reviews have said anything about it, everything I've read has been pure speculation. People were talking about the 9 series back in June/July, and we're just now getting the flagship model soon.
I wouldn't count on the 9800GTX coming out anytime soon. I'd be stupid to wait that long for it.
Realisticty, any card you pick out now's going to be fine. You'll benefit from a few more FPS, but it looks like the 8800GT and up and a 3780X2 all kick ***.
We aren't going to see any game push video cards and computers like Crysis for quite sometime, that came cost millions of dollars to produce and took quite sometime. Far Cry 2's going to be the next one that'll punish machines as much as Crysis did.
My point is: For a bang for the buck, single card solution, get a 8800GTS 512MB. It'll do you just fine for quite sometime.
If I wasn't going to SLI the 9600GT's I'd pick up a 8800GTS 512MB or a 3780X2. Not a 8800GTX.