This morning Microsoft announced that the "Windows 10 April 2018 Update," code named Redstone 4 and known for a time as the Spring Creators Update (at least unofficially) would become available for download on Monday April 30th, and begin rolling out to Windows 10 machines worldwide beginning May 8th.
If you're on the current Insider build 17134.1, which has already been released to the Fast, Slow, and Release Preview rings, you can just install KB4135051:
Are you on build 17134.1? If so, check for updates! KB4135051 is now published and will update you to 17134.5. This applies to all rings: Fast, Slow, and Release Preview. This is a quick download/install. Let us know how it goes!
— Windows Insider (@windowsinsider) April 27, 2018
Typically, an update like this just removes any Windows Insider specific markers, and doesn't add any new features or bug fixes, and this very quick to download and install KB seems to bear that out, but there's no changelog yet, so we can't be sure.
In any case, Insiders should go ahead and install this update, it's quick and (hopefully) painless.Further reading: build 17134.5, Windows 10, Windows 10 April 2018 Update, Windows Insider