CNet published this review of replacing the dual-core chips in a Mac Pro with the latest four-core chips. They found about a 30 percent performance improvement from doubling the number of cores, and that was with rendering apps that are highly processor-intensive and are already multi-threaded. Granted, that was going from four cores to eight rather than from two to four, but the concept of diminishing returns for each additional core still applies. The benefit of quad-core processors for most laptop applications will be 90 percent bragging rights, 10 percent useful performance.

If what you can get now is what you need now, get it now. As previously posted, no matter what you get and when you get it, there will be something better in a few months. That will be as true next year as it is today.