There is a guarantee that this path is stable:

https://github.com/Microsoft/vswhere/wiki/Installing

> This is a fixed location that will be maintained.

"Windows 10 will be the last Windows". Guarantees work as long as they don't change their mind.

Find me one place where Microsoft officially documented that there would be no version of Windows past 10.

https://www.pcmag.com/news/windows-10-the-last-version-of-wi...: a developer evangelist said it at their Ignite conference in 2015, and a subsequent official statement by a spokesperson clarified the context of that statement in a way that strongly implied that it was indeed official policy at the time, but with the explicit caveat that it could change again (“We aren’t speaking to future branding at this time”).

I know this quote. It was said once and the official statement was neither a confirmation or a denial. Which makes sense because why would Microsoft want to commit themselves either way?

Eh. They're basically right. Windows "11" is just rebranding. There's no reason why it couldn't have been a Windows 10 feature update, except that they wanted to drop support for older hardware.