So, maybe I'm misremembering, but wasn't Windows 10 meant to be the forever-Windows? I'm almost sure there was some marketing to that effect from Redmond at the time.
AFAIK there's no official corporate communication to that effect. The whole "windows 10 will be the last windows" thing can ultimately be traced back to something that a evangelist/dev said at a microsoft event. That didn't prevent tech blogs/media from parroting it far and wide though, so that's probably why you might have "remembered" it.
> "Right now we’re releasing Windows 10, and because Windows 10 is the last version of Windows, we’re all still working on Windows 10." That was the message from Microsoft employee Jerry Nixon, a developer evangelist speaking at the company's Ignite conference this week.
So it was a Microsoft employee. But presumably not speaking ex cathedra, then.
It was, until Mac OS moved to version 11 (now 12, and counting). Microsoft couldn't risk being seen as less advanced.
Same reason why Chrome is at version 100 and Firefox is right behind at 99.