No doubt that Fermi (top model) will be a great performer,but don't get your hopes too high. It will beat single Cypress ,but 5970 will be more than enough to take on it. Even a 1Ghz single Cypress will be competitive in many cases.
Fermi design policy was primarily GPGPU computing capability ,after that gaming. It doesn't help that it is huge and power hungry and that it had design issues(Charlie talked about issues NV had early on with Fermi),and it doesn't help that TSMC's 40nm node is not top notch yields-wise.