Neither company is saying when exactly their DirectX 11 cards will be out yet other than Q4 2009. NVIDIA is still mum on 40 nm. Of course we should expect the DirectX 11 cards before Christmas so they can get a boost from Christmas sales.
The 8800 GT is still a great card and can handle HD-DVD/BD playback as well as handle most games well. I have my 8800 GT safely packed back up in its box as an emergency backup card if my ATI 4980 fails for some reason. So what if you can't max everything and run the resolution at the highest level? Yeah, I know it's aggravating. If possible I would hold on to using the 8800 until the 40 nm DirectX 11 cards come out. Save the money. It will suck to spend the money on a card now only to not have DirectX 11 support when new games come out that use it.
If you really want a new card now then go for it but IMHO it's not the most financially feasible decision. Which is the best card to go with is very subjective. If I had an option I would likely go with an XFX ATI Radeon HD 4890. I'm sure others will disagree and say to go with an NVIDIA card but, as I said, it's subjective.