Maybe you should spend a day with me at the office so you can see why this article is absolute horse****.
In the past few years alone Windows 7 has made a killing in sales numbers, Linux is still steadily being improved upon and adopted by users and Mac OS has an ever increasing rabid fan base that swears by it.
Not to mention the looming Windows 8 release which had a ton of people salivating at the idea (and hoping it'll be awesome).
If anything I think that the OS sector is just getting better and better...
Where's this Chrome OS you talk about?!?
Computing from within a browser. Oh hell, just the idea makes me sick.
Personally I see the exact opposite happening. With the speeds mobile devices are currently attaining it won't be long before those stripped down OS's on the current mobile devices are replaced with full OS capabilities. (plug phone in dock, use phone as PC, unplug, go home etc.)
Yes, the "cloud" will be there, but for syncing files etc. I don't see cloud computing as viable, even most developed countries don't have nearly enough bandwidth and low latency to have browser based cloud computing services that can compete with having the power in your palm. Also, the amount of -and life cycles- of legacy systems out there will make sure that the OS goes nowhere yet.
In fact, a massive company in SA just recently switched back to dedicated servers after their massively expensive virtual server environment gave them more trouble than it's worth... yes, it's not exactly the same as cloud computing, but it comes close enough as far as I'm concerned.
If what you propose is actually what'll happen in future, we're still a helluva long way off.