Also, we're flirting with the limits of Moore's "law" here. I did a report back in high school on it and speculated you'd never really see processors over 4GHz. I guess I was right.

As you start to shrink transistors and the spacing between them, the chips get hotter, burn more power, and throw more errors. You also get electron "leakage" where the electrons inadvertently jump between gates, so the processors become less efficient and you have to run extra fault-tolerance to check for the errors.

Multi-core and bringing all the other components up to speed is the way to go for now until a newer technology comes, like quantum computing or light based processing.