19H1, the next feature update for Windows 10, is finally starting to come together. Yesterday, there was a new Windows 10 Insider Preview build in the Fast ring and it finally changed the version number to 1903 from 1809. This number confirms a targeted RTM for March, and a likely public release in April.
Unsurprisingly, Microsoft seems to be using the same naming convention that it's used with the last two feature updates, calling it the April 2019 Update. The news was spotted by Tero Alhonen, who ran a PowerShell script which is commonly used for finding these things.
Note that this does not mean that anything is written in stone. Around this time last year, someone ran the same script and it showed that 1803 was going to be called the Spring Creators Update. There was some backlash over the name, and Microsoft ended up having a change of heart, calling it the Windows 10 April 2018 Update.
It does seem likely though, as Microsoft is apparently done using fancy names like the Anniversary Update or the Creators Update. Sticking with date-based names keeps things a bit simpler, and easier to remember.