A launch date for the NV45 is not know yet, but it will probably be close to the launch of Intel its 775 CPUs and PCI Express compatible chipsets.
Here is what we know. The tech was sampled in February and in April was supposed to be in production. The memory specs will be very similar to the Ultra 6800, NV40. Memory on cards will be clocked at 1100MHz and we know that the plan is to clock this card even higher, if that's possible. The memory type will be 256MB of DDR3 memory with 256 bits, just as in the case of the NV40.Source: The Inquirer
It will sell at an "enthusiast" price range of $499 - not cheap but fast for sure. Did I mention that it's a PCI Express 16X card? Well of course it is, but I expect it to look very similar to the NV40 but I guess they have to clock at least a bit faster, to put some clear water between it and the NV45 and make this expensive upgrade worth it.