Dunnington, an Intel 45nm 6-core Xeon processor is planned, and said to come after Tigerton. Launch is slated for "2H'08". Don't delay purchase of a Mac Pro if you need one now, though.

Some of the specs: 3MB L2 Cache, SEE4, Pin-compatible with Tigerton.

With little imagination, can anyone think of any reason there won't be a 12-core Mac Pro in 2009? I think that a workstation like that could fit rather nicely with a 4K workflow.

http://www.dailytech.com/Sun%20Leaks%206core%20Intel%20Xeon%20Nehalem%20Details/article10834.htm
http://blogs.zdnet.com/Ou/