German hardware website hardware-infos.com has details on what it believes will be the first DirectX 11 from both NVIDIA and AMD/ATI.
Note: It's important for me to point out that these numbers are unconfirmed. That said, they do look convincing.
Radeon HD 5870
Radeon HD 5870 X2
These numbers would make these parts almost twice as powerful as the current HD 4870 and HD 4870 X2 graphics cards.
GeForce GTX 3xx (G300)
These numbers would make this part more than twice as powerful as the GeForce GTX 285.