It shouldn't be allowed to happen. It's almost like letting public infrastructure fail.
Many people regard their computer as an appliance. To be told that you need to spend several hundred dollars to buy a new computer (or less to buy a new OS and find someone to upgrade you) is hard to swallow. From their perspective, it's working perfectly fine - why should they throw away $400? Does that mean they'll have to do it all over again in a few years? My grandfather was especially perturbed by that idea. I suppose I would be similarly perturbed if someone told me I needed to upgrade or replace my dishwasher even though (as far as I could tell) it was working perfectly fine.
(Just to be clear, that's not how I think of it - I am running 8.1 on my old Vista for a reason.)
If MS isn't going to issue patches, there ought to be some way for someone else to be contracted to. Buildings are essentially open source so that is easy to do. Software isn't necessarily.
My point was that most buildings aren't kept around forever either, as you were implying.
How?
Microsoft already issued a patch( not that they didn't support XP a long time over its lifespan ), it is called Windows 7, Apple does this as well, with their yearly OS releases, even though in a more clever way.
Microsoft's support of old crap is already at a heroic level. They've already gone above and beyond what anyone should reasonably expect. If people persist in using old junk well after it's obviously a bad idea, that's their own problem.
A bridge should be maintainable and upgradable forever,just like Linux. Windows obviously was a poor choice to begin with !!!