Great article - maybe because it matches my views :) But it's a realistic response with real details. Most articles only consider the desktop side of things, and yep that's falling but still huge. Server side, for many companies to move away from Microsoft is just not feasable - and not because of vendor lockin, but having to learn so many different technologies and actually spend the huge amount of time and money to migrate. On top of that, a lot of the specialised 3rd party vendors/companies align themselves with Microsoft technologies - how many Office Suite addons are out there, and how many 3rd parties only officially support Microsoft (or even have their app available on a non-MS OS)?
Even if Microsoft fall a long way from where they are, their server side of things will go on for a very long time.