Come on, the post explicitly addresses this -- he is convinced that this telegraphs the future lockdown of the regular desktop, and that alternate means of installing apps will be removed in later versions of Windows.
You might disagree, but don't pretend it wasn't mentioned.
I'm not sold on this telegraphing the future for Microsoft, though. It seems rather odd that Microsoft would destroy one of the major reasons the OS has remained so prevalent and successful: backwards compatibility. This is much the same reason why Intel has never deprecated instructions from x86. If they bring out a new OS that makes it so we can't install our old apps because of the Windows Store, that just gives people more reason and time to consider a different option like Mac or Linux. I just don't think Microsoft would risk such a thing.
On the other hand, I'm not surprised to see the lockdown on mobile/tablet applications. People are already used to this and haven't yet been introduced to true freedom on their mobile devices (besides those of us who have rooted our phones). It'll be interesting to see what happens if some of the new Ultrabook/transformer devices take off.
In the end, we do need to make sure this issue is still raised. You never know, Microsoft might take this step and that would be bad for many developers and consumers.
You might disagree, but don't pretend it wasn't mentioned.