There's a lot of things people have to understand before assuming the inevitable world of ultra portable computing comes in to take over the computing world. Everything is not as it seems, and companies don't want you to see it any other way.
When was the last time you saw someone with a tablet? When was the last time you saw someone with a tablet that wasn't from Apple? The iPad maybe selling well, but not other tablets. HP gave up cause their tablets weren't selling, and BestBuy wanted HP to take them back. In fact, from what I understand is that only Apple has had successful sales of tablets. Everyone else is still trying to wonder why their tablets aren't flying off the self. This means that only Apples tablets are selling, and probably due to it just being an Apple product.
The ultra portable laptops are a result of people not needing the processing power of modern PCs, but why is that? About 10 years ago we really didn't need anything more then 1Ghz for web surfing, email, and word processing. Today, that hasn't changed. What did change is the gaming industry. When the Xbox 360 and PS3 took PC gaming away, so did the need for fast hardware. Most people game on their tablets, as most people did on their PCs. The difference is that no PC game today needs the latest and greatest hardware. If anything, you could use a PC from 4 years ago and still play games just fine.
If you build it, they will come. Make applications that need processing power, and you'll see people coming back to desktop PCs. I'd also have to wonder why we aren't building our own laptops? Their modular just like desktop PCs, but nobody has made a standard to build a laptop around. You know, like ATX for motherboards and cases in desktops.