Is the desktop PC on its way to extinction?

The introduction of laptops, followed by smart phones, net books and now tablets, seems to have started the debate on whether or not the desktop PC is on its way to extinction. Without a doubt, mobile phones and tablets are becoming smarter and they have enough computing power as previous computers which occupied large spaces. But can we say that the desktop PC is on its way out?
I remember, recently, when two of my children were about to start university, both requested for computers to assist in their school work. My first instinct was that they would want laptops but to my surprise, one of them insisted on a desktop PC. I was surprised because I thought it was all about portability and the ability to go mobile. But I guess I did not have the whole story. My son outlined his reasons for the desktop PC. He "wanted to use it for gaming and most laptops and other devices did not have the required specifications." Secondly, the performance and life expectancy of the desktop outweighs that of the laptop. Thirdly, it is easier to upgrade parts of the system unit of a desktop. Finally, he indicated that he worked better in a fixed position with the mouse and keyboard which the desktop had. He had made points which sounded cogent but is this the whole story?