Outside of home use, I haven't used a desktop in years. Every company I've worked for just gives a laptop. But other people have already brought up why I think the phone will take over. Right now, you're viewing a phone as a phone, not as a computer. And you're certainly not alone. Microsoft with their Surface is the only company starting to look into turning a tablet into a PC, and at this time, it's still rudimentary. Why can't a phone hook up to my computer monitor or use a keyboard and mouse and a printer? There's nothing stopping it, outside of the companies not seeing the bigger picture. Yes, all that stuff can be accomplished today, as there are apps and hardware for that, but it's not native to the devices. The general audience is tech ignorant, and a company can't guarantee them buying external packages. But sooner or later, an iPhone or Android could come with a docking station that connects your mobile device to your monitor and makes it a computer. I think it will probably be something wireless, so you never even have to remove your phone from your pocket. You'll just have your computer, as we all have phones. The technology is there already. It just requires a company to realize that the market could be created.
Windows 10 Mobile with Continuum. That "phone with a dock" future came months ago.