Confusion of numbers
Well, maybe. Maybe tablets will outsell PCs. Thing is everton mints outsell Mercedes C-class saloons. Socks outsell underpants 2:1. You aren't comparing like with like.
in 0.5 billion office workers need a desktop PC this year, the fact that each of their children has an iThing, outnumbering the desktops by 2,5:1 does not mean that those 0.5 billion won't want a desktop to do their job next year. It's a class error.
M$ has become deluded into thinking the toys are an alternative, not an extra. If they concentrate all their efforts on the toys, the desktop will suffer.
Oh look. Already happening.