To design a lightweight OS similar to Chrome OS or LinuxMint, Microsoft is now developing a lightweight Windows OS under the codename Windows Lite.
Windows Lite is an unofficial name for the OS and the actual name might differ. It is designed for dual display devices which includes foldables with concept shown above.
Windows Lite would likely appear with similar UI from Windows 10 and allow smartphone connection to PC via Surface Hub. Nonetheless, features are limited as it is designed to be a lightweight system.
As for the launch date, Microsoft is likely to bring this OS on developer conference happening on May.