According to a sleuthing Windows Insiders, the name of the next Windows feature update appears to be named "Spring Creators Update". This is based on the output of a command entered in the latest Insider Preview build from the skip ahead ring.
Yesterday, a Twitter user who goes by the name WalkingCat asked his followers to run the PowerShell command "Get-VMHostSupportedVersion" on build 17618, which the latest skip ahead version available to Insiders. Someone responded with a picture that clearly shows the next update is being named Spring Creators Update with a build number of 1803 and a version number of 8.3.
To explain how this works, it is important to understand the various builds that are available to Insiders. The next version of Windows 10 is codenamed RS4, or Redstone 4, and the version after that is RS5, or Redstone 5. For most insiders, they are previewing the builds associated with RS4, which the next update to to be released this Spring and what this article is about.
There are some insiders, though, who are in the skip ahead ring. This means they are given builds for the RS5 build that will probably be released sometime during the summer of 2018.
Now, the PoweShell command Get-VMHostSupportedVersion lists all the Hyper-V virtual machine configuration versions that are supported on a particular host. This list will contain the name of the previous Windows 10 version. Since the RS5 build 17618 comes out after the RS4 build, when you run this command on it will display the names of the previous Windows 10 versions. This includes the RS4 build that will be released before it.
This is why the output of this command on a RS5 build pretty much confirms that the next update will be called Spring Creators Update.