The computer industry is surprisingly robust in many ways and also fairly good at defying predictions.
I've felt for a long time that computers would get smaller (as they have) but that just like cameras there is no real "one fits all wonder" solution for users.
And right now I'm going to stick my neck out here and go against the grain of most commentators. The growth in tablet computers is ultimately overblown in the long run (it will grow) and it's not a viable solution for desktop or laptop users (they will fit a type of user but they are not replacements for other products). The built in monitor/computer, these make sense for space saving reasons. But also present service issues you're using a laptop shoved into a monitor (bottom line)
Out of all of this it's interesting that the old dated Desktop PC is still around and doing fairly well at that. It's got smaller (in some cases), more swanky looking (v the old beige dull boxes) but it's death was predicted a long time ago, yet it offers a number of obvious advantages. Universal parts are made to a standard and you can get whatever you want for a PC, it is easy to upgrade and service, ultimately the most flexible of all computers, dead monitor? no problem just attach a new one. Over 10 years ago people were saying that the desktop was doomed and that nobody would want one as laptops would be so cheap (and they are cheap) didn't happen..people buy both depending on their needs
I honestly don't expect it to go away any time soon.
As for Apple the same applies as to the PC industry
The desktop computer is a bit like the DSLR bemoaned by some, but the old horse just keeps on pulling and shows no sign of packing it up for the dog meat factory