https://wccftech.com/microsoft-forks-windows-10-rs5/

As we just reported, Microsoft has started thinking about the version of Windows 10 that will be released in Spring, 2019. The company announced almost hitting the finish line as far as new features for Windows 10 RS5 are concerned. While Microsoft will continue to work on fixes, improvements, and performance stabilization, it has forked the upcoming Windows 10 RS5 into its own branch called “RS5_RELEASE” just like the previous branches.

This means that soon Skip Ahead Insiders would be able to test 2019 Windows 10 features (more details on that here). But it doesn’t mean that Redstone 5 is all done and dusted. By looking at today’s feature improvements, by no means does it look like Microsoft is only thinking about stabilization since this is one long changelog.