There should not be any XP at this point in time.
The sad thing is they aren't getting security updates. If it was open-sourced, then people could keep their systems secure.
edit: If you are suggesting that users would go back to XP once it's opensourced then you don't have much faith in people.
That's a good number of people, I think. I would love to see them empowered to maintain their computers however they want.
Security updates don't magically happen. But with open source, people who want to do them can put in the effort. That's the point. You could maybe sustain a business of being paid to maintain security updates for this magical open-source-XP. Or maybe some enthusiasts would choose to do it. Maybe they wouldn't. But we'll never know, because opens-source-XP will not exist.