Hard for hardware manufacturers - not so for the rest of us
Sure, like cars, the replacement cycle is getting longer. Also like cars, there's no longer status value in a PC, possibly the opposite bar gaming rigs. And indeed PCs are "competing" with more devices. Further, a senior bloke at work has tried to switch to tablet working.
However, for some things a tappy keyboard is a necessary thing. I'd like to see my kids complete their projects on a tablet. Also, though it chews time, Candycrush and iPlayer is not killing the PC. And for the tablet bloke, I giggle every time his iPad falls over in a meeting, And his presentations are even more sh*t than the standard ppt stuff.
As it happens, amongst other things we run a 10-year old XP laptop that the wifey prefers because of the proper (not wide) 15" screen and 1440x900 res. Stripping everything has made it boot fast. The much newer Windows 7 (widescreen) laptop reluctantly does Skype duties only.
I don't love M$, but the PC death is over-rated. At least in my western eyes.