Advancement is governed by economics as well as technical capability. There must be demand for new technology, or a field stagnates. Witness aviation as an example... utterly stagnant outside of military niche applications.
People seem to no longer want faster and faster computers, and the market seems to be moving toward lighter-weight lower-power portable devices like netbooks, the iPad, etc. Those have slower CPUs than current-generation desktops. I suppose the extreme gamer and server/datacenter markets are still driving performance, but for how long?
One problem is that programmers are not using the capabilities of current-generation processors, partly because the dominant OS (cough Windows cough) makes it horrifically painful to deploy desktop apps. This drives all development to the web and turns desktops into thin clients. In the end this kills demand for performance outside the datacenter market.