What will be impact of Google Contact API deprecation?

According to Google, Contact API will be deprecated on June 15, 2021. Developers should use "People API" (published in 2016).
I am trying to understand what will be impact of this change on old Android phones (Android 4.4 and below).
Does it mean that these devices will not be able to sync contacts with Google account?

 

It is much worst than this. Contact API will not work on all Android devices, not only on new devices because this is server side change. Server/Endpoint responsible for Contact API will be shut down and any attempt to access it will be responded with "404 not found". The same as with old SyncML service.

It means many apps on old phones will stop working because either developer will not update these apps with new API (abandoned apps) or updates will not be pushed to old phones for multiple reasons (not built for old Android versions, hardware or software limitations).

Main question here: Will built in Contact app (whatever it is called on different phones) continue to work after the change?

Regarding deprecation of old software (Android Market, for example): it is understandable and not an issue in this case. First, this change is server side change and not related to Android (any platform can use Google APIs). Second, I do not really expect devices on Android 2.x-Android 4.0 to be something more than dumbphone anyway. They can not connect to Google (well, 2.x can not, I did not check 4.0) and, actually, can not be used as smartphones. But this change may affect newer devices - at least 4.1-5.0.