I got an email this morning (pdf attached) from G Suite saying that they're removing support for password authentication for apps in favor of oauth only.
* June 15 2020 - Users will be unable to create new app passwords
* February 15 2021 - All existing app passwords will be disabled
The email suggested that existing passwords used for SMTP will continue to work for some time, but made no promise of continued support and suggested migrating SMTP to oauth as well.
Links that may be helpful for developers: