I'm waiting for the Nvidia 300 series for a few reasons.
1) Nvidia isn't going to release a "New" card that doesn't outperform it's previous Top of the Line card.
2) I think the new ATI cards are going to be replaced with another new version sooner than most people are expecting, much like Nvidia did with the 9000 series of cards.
Here's my reasoning. ATI released the 5870 and it is easily keeping up with the GTX 295 in most benches and it's close in the ones the GTX 295 is winning. The GTX 295 is a Heat Monster and Driver Performance is already Max'ed out or very close to it and it's only a DX10 card. So it is easy to expect the 5870 to improve in Performance as Driver Development ages. So why has ATI already released the 5970? Just to beat the GTX 295 soundly? I don't think it was necessary to do so and what are they going to do when the Nvidia 300 Series is released? I think they already have or they are very close to a new and improved version of their current gpu's and they are just waiting on Nvidia. So I'm waiting 2