According to the traditional plans of Microsoft, Windows 10 v2004, or rather the May 2020 Update, should arrive by the end of May or in the first half of the year. At first it was expected for May 12th, but according to some information leaked online it seems that a more likely date is May 28th. The indiscretion was somehow confirmed by Microsoft itself, within an official page.
The company has been working on the update for more than a year and recently published the images on the Windows Insider Release Preview channel. This, however, does not mean either that the operating system has been released to the general public, nor that a date for the final roll-out has been revealed. However, the company has shown a three-day window in which it could launch the next "feature update": May 26th, 27th and 28th 2020.
The dates can be read in the 2020 Driver Shiproom Schedule, a document that Microsoft addresses to manufacturers to ensure that the latter do not release driver updates on inconvenient dates, such as shortly before or shortly after the arrival of the patches of Microsoft and major updates. The goal is to avoid conflicts between updates by aiming to increase their reliability (thorny topic with the latest versions of the operating system).
The news in the Driver Shiproom Schedule does not necessarily suggest the final release date, however it can be a very precise indication of the timing envisaged by Microsoft. It is worth noting that it would be a serious disservice to indicate an incorrect date to the OEMs, and that in the 2019 Driver Shiproom program Microsoft had marked the dates of 21, 22 and 23 May 2019 for the update to the 1903 version which was finally released on 21 May.