Lol the desktop pc in one form or another is here to stay at least for the next 20-30 years minimum. This is probably the lamest speculation article I have seen on the subject in a long long time. Computer gaming magazines (such as Computer Games) did similar articles back when the PS 2 was released stating it was the sign of the times for pc gaming because consoles were so powerful now and easy to use blah blah blah. Same old stupid bullshit speculation, except now we swap game systems for tablets etc.
Pc technology sales will rise and fall. People en masse are not just going to keep buying new computers every 6 months to 1 year. A lot of people are still using their older Core2Duo and Quads and Phenom X4 setups from 3 years ago and simply dont need another setup or OS yet. These are the same types that used their single core Athlon XP Compaqs and Pentium 4 Gateway towers for 3-6 years or more also. They wont upgrade until they absolutely feel the need to, or until their tower dies. The Windows market would look stronger had Vista not been released, but as is, Microsoft is having to deal with the fallout from that.
Even with all of that going on you still have tons of people buying pcs for the first time, or giving their systems to their kids and buying new ones. That in itself makes up a nice chunk of the market for desktops and laptops. In addition to all of that, you still have the custom builders out there buying hardware, and vendors selling custom builds, so that should be taken into account. You dont exactly hear about Asus, Biostar, ECS, MSI, etc stating they are hurting bad right now ehh? The Pc market may not be in 100 percent excellent shape right now, but its in no way bad off either, not at all. Its doing fine, and its going no where any time soon.