Microsoft has changed the minimum storage requirements for the Windows 10 May 2019 Update, to be released publicly next month. In an updated support document on Microsoft’s Hardware Dev Center website, the company indicates that both the 32-bit and 64-bit versions of Windows 10 version 1903 will require a hard drive with 32GB of storage or greater (via Pureinfotech) .
Windows 10 version 1809, aka the October 2018 update currently requires 16GB of strorage or greater for the 32-bit version, and 20GB or greater for the 64-bit version. The support document doesn’t give an explanation for the higher minimum storage requirements for the May 2019 Update, but this could be a consequence of the new Reserved storage feature that will take around 7GB of disk space for system updates.
It's pretty rare these days to see PCs with just 32GB of storage, so this change in hardware requirements shouldn't affect many consumers. The Windows 10 May 2019 is still being tested with Windows Insiders on the Slow and Release Preview ring this month, but Microsoft recently made ISO files available on MSDN. If everything goes well, the public rollout should kick off in May, but the software giant may well release a couple of bug fixes updates in the meantime.