Windows 10's upcoming UI, previously known by its code name "Project NEON", now has an official name. At yesterday's Build 2017 event, Microsoft introduced it officially and also released an updated SDK for Universal App developers which supports new APIs. The new user experience APIs are called "Microsoft Fluent Design System".
Microsoft has already released a bunch of preview builds for the next major Windows 10 update (codenamed Redstone 3) to Windows Insider Program members. They are now actively working on adding new features as well as those features which were postponed from previous releases. This includes the Project Neon system-wide redesign and the MyPeople bar. However it is unclear at this stage when Microsoft is planning to release the final version of this update to the masses.
While Microsoft is busy working on the next major update for Windows 10, named Creators Update, there are rumors floating around about the next wave of Redstone updates and its features. Microsoft is in the planning stage for the next major update right now and one of the the internal presentations has leaked into the hands of some beta enthusiasts. From the concepts in it, we now know that Microsoft is planning to evolve the current Metro Design Language 2 used in Windows 10 into something new, codenamed Project NEON.