https://www.techradar.com/news/windows-10-s-mode-is-coming-and-microsoft-has-big-hopes-for-it

Microsoft has clarified how it intends to proceed with turning Windows 10 S into a ‘mode’ rather than a standalone variant of the operating system, with the change happening in the next (imminent) big update for Windows 10 – and the good news is there’ll be no charge to upgrade from ‘S mode’ to the full-fat version of the OS.

In a blog post, Joe Belfiore, Corporate VP of the Operating Systems Group at Microsoft, also confirmed that S mode would be applicable across all versions of Windows.