If it were that simple, it would have happened already.

There are still a lot of businesses that, unfortunately, depend very heavily on Windows XP for their ongoing operation. The cost associated with switching may far, far exceed any benefit it could bring.

We aren't talking about a couple of Ruby on Rails developers sitting in a cafe using MacBooks. We're talking about global organizations with tens of thousands, if not hundreds of thousands, of computers. We're talking about applications that will only run properly on Windows XP. We're talking about astronomical costs that will bring only comparatively minor gain. That's the kind of situation that does not lead to change.