Yesterday, Joe Belfiore, Corporate Vice President in the Operating Systems Group at Microsoft, revealed on Twitter that Windows 10 S becomes 10 S mode in 2019. However, today that revelation got clarified and we probably won't be waiting until 2019 to get S mode.
Windows 10 S is a restricted version of Windows 10 that only allows software installs from the Windows Store. In a post on the Windows Experience Blog, Belfiore explains that Windows 10 S was introduced to deliver "predictable performance and quality" and more than 20 devices shipped with it installed. However, the naming apparently caused confusion so Microsoft decided to simplify the experience.
The next time Windows 10 receives an update, S mode will be introduced. The key thing here is, Microsoft views S mode as a way of offering better security, faster boot times, consistent performance, and longer battery life. Windows 10 Home, Pro, and even Enterprise will have S mode available, but also the option to switch out of S mode with no charge and at any time.
One thing that isn't clear is whether you can go back into S mode once you've left it. I've asked Microsoft for clarification on this point and will update this post once I get a response. I can see a return to S mode being difficult to achieve as you may have apps installed that aren't from the Windows Store. What happens to them if you are allowed to switch back to S mode?
For consumers, it means purchasing a new PC or laptop advertised as using Windows 10 S mode should not cause concern. You can disable it and get the full Windows 10 experience at any time and without spending any extra cash. However, for parents, S mode will likely be something they want to keep active for the extra protection it promises to offer.