Microsoft's rumored Windows Core OS is becoming increasingly more likely by the day, as references to the software can be found in Microsoft's own support pages. Given the timing, this may even be the "experience" we see at Microsoft's event in October.
Windows Core OS is, reportedly a modular operating system that can run on dual-screen devices. Windows Latest actually discovered the references to Windows Core OS in this support document from Microsoft that details basic level Windows diagnostic events and fields for version 1903.
The reference can be found in the Common Data Extensions.utc section and states via two separate bullet points "wPId The Windows Core OS product ID" and "wsId The Windows Core OS session ID." This document has actually been sitting around since April 22, and no one has noticed the references until now (not surprising, since the document is a 274-minute read).
We'll be on the ground at Microsoft's October Event, so stay tuned for more info, news and hands-on reviews.