Nehalem's Chief Architect, Ronan Singhal, has confirmed Fudzilla that Nehalem will get its eight-core version in the second half of 2009.

We also learned that such a chip will be more than twice as large as the quad-core Nehalem and that we should expect TDPs around 150W level. The chip will have much more cache than 8MB that you see on Quad-core Nehalem-EX, the server part.

Eight-core Nehalem would definitely have a lot of cache and it will come at significantly lower frequency compared to the highest clocked quad-core Bloomfield CPUs. We also learned that such a chip will be announced, used and sold as a server / workstation part and that Intel is investigating whether it makes sense to launch such a chip for desktop market.

At this point its unlikely that eight-core Nehalem will make it to desktop, as in applications such as games it could easily end up slower than quad-cores, due its lower clock.

You should look at this chip as a Dunnington 6-core successor and eight-core Nehalem will end up as a 45nm chip.