It looks like 2021 will be a big year for Windows 10 as Microsoft plans to release a massive feature update with major updates to refresh the design for the various elements of the operating system.
According to Zac Bowden of Windows Central, Microsoft is working on a big Windows 10 project codenamed "Sun Valley" that will provide a major user interface (UI) update for many UI elements such as the Start menu, Action Center, and even File Explorer, using consistent modern designs, the best animations, and new features.
These new features are expected to be launched with the second Microsoft feature update released for Windows 10, usually in the fall known as the "H2 Update", in this case, version 21H2, while the first update (version 21H1; codename Iron) which Microsoft started developing it last year, it's supposed to be a minor update with only small changes and features, and this has been verified well with the latest version of Windows 10 Insider Preview released last week (version 20246) that defined the switch to the "fe_release" branch instead of the "rs_prerelease" branch, as well as deleting several pre-tested features in previous months in Dev Channel builds such as the updated emoji picker, redesigned touch keyboard, voice typing, and theme-aware splash screens.
The switch to the branch "fe_release" means that the development of the next Windows 10 feature update is almost finished, and no major changes will be made to the upcoming builds on this branch, and Microsoft will likely release a preview build to the insiders in the Beta channel ( formerly known as Slow Ring) soon after fixing the major known issues in this release, as the builds from this branch are stable enough to test.
Delaying those new features until next fall gives Microsoft additional time to develop and test them in the Dev channel, and those UI changes will bring a lot of user interface elements found in Windows 10 X, Microsoft's version of Windows 10 for dual-screens, as Microsoft promised previously to bring them first to the one screen devices such desktops and as 2-in-1 devices, Where the first Microsoft dual-screen device (the Surface Neo) it is expected to be released in spring 2022.