I think MS understands the problems inherent in a fractured user base much like Android has become since somewhere around version 2.X, and is making the effort to bring in as many as possible under the Win10 banner.
To do this they need to do two things 1) make it BETTER than 7 and 8.X, and 2) make it so cheap (free) that everyone will want to jump on board. Once they have a substantial fraction of the user base, they can more easily abandon older versions. They are hoping that they can do it in a year; we'll see.
It's interesting that they didn't include XP and Vista in the free upgrade, does that imply that they will abandon those in any case as they have been threatening to for years?
|