Starting with Windows 10 2004, Microsoft is changing the minimum hardware requirements for the device. The change affects new, not existing PCs from OEMs only.

According to the documentation (thanks to @TeroAlhonen for the link), Microsoft isn’t making available copies of 32-bit Windows 10 media. For now, Microsoft is still allowing users to buy 32-bit Windows 10 at retail and to continue to get updates for their existing 32-bit Windows implementations. Anonyone with a 32-bit PC should be fine for as long as their devices remain usable. 

From Microsoft’s documentation on minimum hardware requirements for Windows 10 desktop editions:

“Beginning with Windows 10, version 2004, all new Windows 10 systems will be required to use 64-bit builds and Microsoft will no longer release 32-bit builds for OEM distribution. This does not impact 32-bit customer systems that are manufactured with earlier versions of Windows 10; Microsoft remains committed to providing feature and security updates on these devices, including continued 32-bit media availability in non-OEM channels to support various upgrade installation scenarios.”

This is just a first step on what’s likely to be a long and drawn-out process of making Windows 10 a 64-bit only product. 

Microsoft is expected to start rolling out Windows 10 2004, the May 2020 Update, on May 28, sources say.