Afaik tesselation specifications of DX11 differ from the tesselation unit of AMD DX10.1 cards, so they probably won't be able to run DX11 tesselation. (even if they could technically, it remains questionable, wether the activation of only one DX11 feature will be possible, though the likelyhood of DX10.1 modes in games rises a fraction)

The GPU is equipped with an extra feature which is not part of the current DirectX 10.0 specification. It contains programmable tessellation units, similar to those within the Xenos GPU (codenamed "C1") also developed by ATI. This unit allows a developer to take a simple polygon mesh and subdivide it based on a curved surface evaluation function, with different tessellation forms as Bézier surfaces with N-patches, B-splines and NURBS, and even some subdivision surface techniques, which usually comes with a displacement map texture.[4] Essentially, this allows a simple, low-polygon model to be increased dramatically in polygon density in real-time with minimized performance loss. Scott Wasson of Tech Report noted during an AMD demo of the technology that the resulting model was so dense with millions of polygons that it appeared to be solid.[2]

This unit is reminiscent of ATI's earlier "TruForm" technology, used initially in the Radeon 8500, which performed a similar function in hardware.[5] While this tessellation hardware is not part of the current OpenGL or Direct3D requirements, and competitors such as the GeForce 8 series lack similar hardware, Microsoft has included Tessellation as part of their D3D10.1 future plans.[6] The "TruForm" technology from the past received little attention from software developers and was only utilized in a few game titles (such as Madden NFL 2004, Serious Sam, Unreal Tournament 2003 and 2004, and unofficially Morrowind), because it was not a feature shared with NVIDIA GPUs which had a competing Tessellation solution using Quintic-RT patches which met with even less support from developers.[7] Since the Xenos contains similar hardware, and Microsoft sees hardware surface tessellation as a major GPU feature with proposed implementation of hardware tessellation support in future DirectX releases (presumably DirectX 11),[6][4] dedicated hardware tessellation units may receive increased developer awareness in future titles. It remains to be seen whether ATI's implementation will be compatible with the eventual DirectX standard.

Wow! Is Pripyat gonna sell DX11 cards or what?!

Look at that side by side character shot. The DX11 version has a real, round filtration unit on its gas mask while DX10 doesnt and, a real, round helmet! Talk bout the magic of DX11.

Now i know i have to chuck my 4870 and get me a 5870.