Windows Insiders in the Skip Ahead ring can expect to receive 'Redstone 5' builds shortly. With 'Redstone 4' (RS4) almost ready for rollout in a month, new RS 4 builds will henceforth be released in the 'rs4_release' branch.
https://www.notebookcheck.net/Windows-10-Redstone-5-starts-appearing-on-BuildFeed.282716.0.html