The author does sound like a retro-grouch. As I often say to hipsters on fixies, “For you it’s retro, for me it’s nostalgia.” That being said, the post-PC era does not mean that nobody has a PC, it means that people don’t have to buy PCs to do non-PC things. Imagine if you needed a PC to watch television. It’s the same thing with email, FB, and web browsing. Why do I want to know how to format a hard drive to read Hacker News?
Steve Jobs described PCs as being like pickup trucks, and he described post-PC devices as being like all the other vehicles people use, from bicycles to SUVs. None of those made the pickup truck go away, and for that matter there is a sizeable market of people who take pride in driving a pickup truck even though they never haul anything bigger or dirtier than a chest of drawers in it.
PCs will be the same way. Available and cheap if you need one, and also available for those just like the status symbol of being a touch guy who fdisks and bash scripts and thinks curl beats Firefox.