Windows 10 ‘Sun Valley’ UI refresh, otherwise known as’version 21H2′, is reportedly arriving in the second half of this year. Microsoft plans to update the existing Windows 10 Sun Valley update with additional improvements like dark properties for the File Explorer. Microsoft also plans to improve the Start Menu, Taskbar, Action Center, and more, which we have outlined below. Windows 10 will be released in the fall of 2021 after Windows 10 21H1 is released in spring followed by Windows 10X.
Source: https://www.bleepingcomputer.com/news/microsoft/the-windows-10-sun-valley-design-refresh-heres-whats-coming/