The "upcoming" Windows 10 version 1803 (that stands for March 2018 release), unofficially known as the Spring Creators Update, *STILL* hasn't been released by Microsoft!
Despite running almost 2 months behind schedule, the 1803 moniker is still being used by MS to describe this build, although the update hasn't been officially given any name.
It's widely expected that Insider Preview build 17134 will become the fabled 1803 release, but even that is not yet official.