Um, even if they sell a PC for $2000, you can replace a chip without buying a new monitor and case O_o
If they had a 10 GHz processor, they’d also be completely dominating the server market. No way in hell they would skip out in that.
But back to the point… there are always theoretical limits to how fast things go. At this point, however, there aren’t too many uses where a 5.0 GHz processor would be more effective than a 3.0 GHz processor, the sole exceptions being data analysis, servers, possibly gaming, video editing and rendering, etc. For a few reasons. One, most of the population doesn’t use anything that requires more than 500 MHz, much less 3000 MHz, much less 5000 MHz. For two, the rest of the computer is already running so much slower than the processor that you generally have a lot of idle processor time while opening a file from the hard drive or even accessing RAM.
Lastly, a LOT of people are looking at changing the way processors work, from getting rid of the processor entirely, or maybe dividing the processor up into several hyper-specialized sub-processors (nVidia is pushing for this), or tandem multi-processor units handing different tasks (subtle difference), or changing the materials to using light or organics, or moving away from binary entirely and going to a base-4 or something. The concept of a silicon binary CPU could be laughably funny in a decade. More than even all that, a lot of people are looking at so-called “clockless” processors. You can look into research on processor technology for years and still not know everything. Technologies are the biggest thing since sliced bread one day, and never heard from again.
The best thing you could do is follow techie hardcore enthusiast websites like http://www.arstechnica.com/ and http://www.hardocp.com/ that cover the latest advances, theories, news, announcements, roadmaps, white papers, research, tools, prices, companies, etc daily.