I'm going to have to jump in here and disagree with this as well. Basically there are two types of computer users. I will call these two types "Casual Users" and "Serious Users." Casual users basically do things with computers like browse the Internet, listen to music, read e-books, and play casual games. Serious users do things with computers like develop computer programs, make 3D models, edit films, and play serious games. It is indeed true that at some point in the near future, casual users will no longer feel the need to even own a desktop computer. They can do basically what they want to do using a mobile device. Serious users will not stop using desktop computers any time in the foreseeable future. Serious users require things like full-sized keyboards and mice, large monitors, swappable and customizable components, easy upgradability, and the extra power that can be gotten from a full sized computer.
It is completely incorrect to say something like "The future of games is the mobile market." The future of casual games is the mobile market, yes, because casual users play casual games, and they will eventually ditch their desktop computers. The rest of us will be playing computer games for a long time to come.
Server Computers are better for 3D models, editing films, and can be utilized for high end gaming, but can also handle multiple users too. And even "serious users" have mobile devices which can currently output 7th gen console graphics. And any advances in the 8th gen with streaming will directly benefit these mobile devices.
So just from that level alone you'll be getting rid of your desktop in favor of a Server which is customizable, easily upgradable, with swappable compnents and in general far superior to desktop. Instead of having a desktop you'll have a Server room where the server computer is and then some sort of desk top area. It's not that the Desktop will die, it's just that it will merge and separate from where you personally are and transform into a server. Then you'll have your own UI port thing which is your tablet/phone
The big problem is the mouse/keyboard and monitor. First, the monitor is sorta a joke in the near future. OLED technology, Holographic technology, pixel paint technology, and pixel lenses which will all be available within the next 10 to 20 years make entire monitor situation silly. Depending on the previously listed tech there screen sizes are pretty much anything practical to infinite and so yeah... >.> not really an issue.
In terms of Mouse and keyboard. I agree. I prefer a mouse and keyboard. Some people don't (they're insane imo), but the keyboard is solved with currently out technology where you can project a keyboard made of laser beams on any surface any where, I think of any size and it is incredibly portable. Though not perfect as having a physical device is still great, but there is no reason to not have a wireless keyboard there that could connect the same as we do now. The mouse on the other hand is a bit of a problem. There are possible ways to possibly get there, but I'm not sure how well those would work, but again, you can just have a wireless mouse.
I'm not saying you're going to be doing all your computing on this dinky 6" screen or whatever tablets get up to... I'm saying the way you conceptualize the mobile devices and desktops is wrong, because that isn't going to be anything like that very very very soon.
We have lots of computer needs in our house holds, we're eventually going to centralize them and our computing technology will continue to advance along with out mobile tech and we'll want to transfer things around so it's just a natural evolution to have server stuff and and wireless stuff... and because this stuff will be linked together people will just naturally have highly capable machines.