There is no "version of Windows you can own". Windows is proprietary software and Microsoft can (if/when they choose) make copies of Windows behave in ways we've already seen (forced "upgrades" switching to Windows 10, ignoring a user's privacy setting even at its most ostensibly privacy-preserving value and chatting on a network anyhow, and more) and ways we can't predict precisely because that is the nature of proprietary software (non-free software, user-subjugating software). Technically speaking, there's nothing preventing Microsoft from issuing an update that would make Windows 7 stop running on or after a certain time/date. They could bundle this code with an update that fixes something important to the user, effectively hiding it from the user and tricking the user into installing that code thinking they're getting a fix for something else (and thus tempting even offline Windows users into going online to fetch the update).
Microsoft could have already issued such code before. There is no way to tell if this has happened without doing the inspection work proprietary software prohibits us from legally doing. And in the event someone finds Windows does something users don't like there's no way to legally improve the code (again, proprietary software restrictions), or legally share those improvements with others, all because these are the restrictions of proprietary software. Proprietary software effectively holds users separate and helpless to have a "version of Windows you can own" and treat yourself and your community with respect and dignity.