Charlie Demerjian from The Inquirer heard whispers at the Intel Developer Forum that NVIDIA might announce a x86 processor at NVISION next week. I find it hard to believe though, technically it should be possible for NVIDIA to make x86 chips but the problem is that it's very unlikely they'll get a license from Intel to do so.
The problem NV has is that both major x86 players have a lock on the technology, and they don't want any new players in the mix. VIA certainly has a nice part with the Nano, but they barely got out under the threat of a lot of legal fighting, and Nvidia certainly doesn't have the x86 patent leverage VIA has. NV is basically locked out unless Intel and AMD both decide to be magnanimous, and we would not recommend holding your breath waiting for this to happen.
That leaves the lawsuit option open, and again, it is hard to imagine them being that self-destructive. Any attempt to enter the market without a license would bring down Intel legal on them like flying monkeys blackening the sky. It would get ugly. Really ugly. Expensive too.