That is according to Jim Turley of Silicon Valley consultants SiliconInsider, http://www.electronicsweeky.com/Articles/2010/10/12/49627/mutlcore-has-hit-the-speed-limit.htm.
I agree with most of his points. Memory is the major bottleneck, and trying to make a sequential program magically parallel fails.
But, power savings? Maybe we can bring back the TURBO button. This time it will actually turn on the extra two cores on the quad-core processor. Cool.