Although we know that NVIDIA is working hard on the new GT300/Fermi cards we still do not know is when they will actually be here. The issue is not one of a single product launch but more a problem of multiple products.
The first to launch will probably be the DX11 gaming parts. These should hit by the end of the year, or at least launch and then be available in shops early next year (2010). The next are the professional cards; the Quadros. These should hit sometime around Siggraph (say April), and the last are the Tesla cards. These are the computational monsters that even now are catching up to the world's fastest supercomputers.
Here we have some extra information. It seems that NVIDIA will be launching the new Tesla 20 series should hit this spring (perhaps also in time for Siggraph). They will not come cheap though. Expect the 3GBC2050 to run about $2499 and the C2070 to hit as much as $3999. Meanwhile the heavy hitting S2050 and S2070 (1U units that allow multiple C20 series chips to work together will run you a cool $13 and $19k each.