Microsoft released Windows 10 in 2015 and followed suit with Anniversary Update in 2016. In early 2017, Microsoft announced that it would have two feature updates each year, one in the spring and one in the fall. At the time, company executives said there would be no "Windows 11" or "Windows 12".
We now know that Microsoft is working on the "next generation of Windows", codenamed "Sun Valley" and that it will be officially unveiled on June 24, before the public release this fall.
But Microsoft seems to have mistakenly published a support page for the upcoming Windows Sun Valley update before it was officially announced.
Yesterday, a publication of a Microsoft support document accidentally revealed that tests were underway for the "Windows Sun Valley" update.
As you can see in the image above, it looks like Windows Sun Valley will coexist with Windows 10.
This means that Microsoft will continue to support Windows 10 alongside this new operating system. In fact, there is a possibility that the company will make two different updates this year, one for businesses and one for the general public.
This support document has now been edited to remove the "Windows Sun Valley" line, indicating that Microsoft did not intend to let it leak. But Microsoft support documents are kept on Github, and the report leaked to "Sun Valley" can be verified, from the Microsoft repository.
Unfortunately, the company website does not disclose more information about the Sun Valley Update and we do not know if the company intends to name the next big update "Windows 11" or "Sun Valley".