Desktop computers should be available for a very long time. Most gamers still want a gaming computer and it would be kind of hard to play some computer games on a cellphone or a tablet computer. The gamers typically want a desktop computer.
Businesses are not going to toss hundreds of millions of perfectly running desktop computers into the trash. Especially in these hard economic times. They will get their money's worth out of the computers they own now.
And companies like Newegg are still in business and a person can still buy computer cases and computer parts and build their own computer. I doubt if Newegg is going to be out of business in the next few years.
Windows 7 will eventually not be available although the last time I went to Newegg it was still possible to buy an OEM copy, which legally can still be used in the construction of a new computer for sale. Microsoft had to back up a little with Windows 8.1 and Windows 8.1 can still be setup to work as a desktop computer.
And Apple is still building desktop computers and just recently came out with a new Mac Pro, which is of course very expensive. But Apple shows no sign of suddenly trashing all desktop computers although of course nobody knows what Apple will do next.
For some people who have limited real needs for a computer a tablet computer or even a cellphone is fine. Some of those people might get very tired of a tiny screen after a while if they do any real work on a computer. I kind of look at a tablet computer being kind of a toy for adults. A fad. If I owned a tablet computer I would want to be able to dock it at home so that a larger monitor, my printer, and scanner, were already connected to the dock.
Apple created new markets to make a lot of money. They came out with the iPhone, the iPod, and the iPad, etc. But once they face competition from others Apple has a hard time competing. Don't believe it? Do a little research. Apple has huge competition today in the small computer (tablet) area and Apple had to reduce the cost of iPhones, or at least sell more older style cheaper iPhones. I think it was Steve Jobs who started to push this idea of the mobile computing lifestyle. Or at least he was one of the ones who did so. Steve Jobs also said that the DVD was dead. But it is pretty cheap to convert your music to mp3s and burn a CD and play your music on a CD player in a car. There are costs involved in buying music online and buying an iPod and getting locked into buying a brand that people do not consider. There are very good reasons why some people want you to get away from CDs, DVDs, and Blu-Rays. They want people to have to buy music from them, buy their equipment, etc. But if you are burning your music to a CD you don't have to use a certain brand, like Apple. You can burn your CDs using a Sony computer, a Dell, whatever.
Apple has really been working recently on various equipment such as iPhones, iPods, and iPads. But in my opinion they may well start putting more effort into desktop computers. Because competition in the small computer and cellphone fields is very tight. Do your own research. According to what I found out the sale of iPods and iPads is down and Apple has been selling older, cheaper model iPhones. Competition is very tight. Apple did not come out with a new, expensive Mac Pro for nothing. And it certainly appears like they have every intention of continuing to build desktop computers and continuing with Mac OS X for those desktop computers.
The so-called post-PC world is total nonsense. Sure there are small computers like the tablet. But there will be desktop computers far into the future, at least until some sort of technology might change that.
I burn my mp3 music onto CDs. I can do that with my old Windows computer. And I can play that music cheaply on CDs in my car. And I don't have to buy into a certain brand or have certain equipment. I say be free.