The May 2019 Update will spend a month in the Release Preview ring

[Windows Central]

Windows 10 '19H1,' known as the May 2019 Update, will spend over a month in the Release Preview ring before rolling out to the public.
Microsoft today announced that it will begin testing the upcoming Windows 10 '19H1' release, known as the Windows 10 May 2019 Update, in the Insider Release Preview ring for over a month, starting next week. This is double the time previous feature updates have spent in this ring, and Microsoft is doing it to ensure the upcoming version of Windows 10 is stable enough for public release sometime in May.

Full story from the WindowsCentral blog...