Like go from 4Ghz, to 8 Ghz, then all the sudden to 20Ghz.
Problem with your statement is you have a sort of duality to think about.
If all you want is a faster processor for is to play games, there's a threshold at which changes become less and less noticeable and relevant as you are less and less capable of perceiving the differences.
From a game perspective, there is a limit to how much you can interpret and deal with, and how fast you can deal with it.
Now, if you're not just doing home computing and want to do heavy calculations and simulations, you don't need to wait for the 20GHz processor...the capability is already here, and many times that. It's called supercomputing, and is done to phenominal degrees every day.
If you're wanting to limit things to just the advances in technology's parts (processors, drives, etc) you'll find that the current technology has decreasing capacity to continue a trend of growth like it has seen in the past. There will have to be a change in the way things are made, designed, and operated, before dramatic changes come about.