If all you do with a computer is read email, surf the web, and read facebook and twitter, well, yeah.
But if you want to do any serious work, like software development, financial analysis, circuit design, medicine, video processing, audio processing, CAD/CAM, real-time processing, astral or nuclear physics development, or chemical engineering, you will need a big screen with high resolution, lots of CPU power, terabytes of local storage, multi-gigabytes of memory, and a honkin’ power supply to drive it all.
None of these things is available in any hand-held device of which I am aware.
I see the typical non-technical PC morphing into the hand-held appliance, and the high-end PC morphing into the workstation.
But the PC, per-se, is not going away, and Microsoft, which supports serious working applications in all the abovementioned fields, isn’t going away, either.
You’re really straying out of “PC” territory there and well into full-on workstation territory....
....which is a point missed by most on this thread, so don’t feel bad about it. The man is right: we’re in a post-PC world where most people....MOST....can do all they need to do on a tablet or smartphone.
Power users still need workstations. For those reading this that insist they do the heavy lifting with a desktop PC, let me remind you that your state of the art desktop today is FAR more powerful than very high-dollar workstations of, say, 5-6 years ago (maybe less, actually).