Google have announced their intent in deprecating the current management API’s in favour of work profiles
We understand that for some organizations this switch may take time so we will have developed an extended timeline for the transition. Device admin API will be supported through Android Oreo and existing functionality will continue to be available in the next major Android release, though device admin APIs for password enforcement will no longer be supported. In the following Android release, expected in 2019, the APIs for password enforcement will no longer be available. We strongly recommend that businesses plan to move to work profile and managed device APIs. By sharing this update early, we aim to provide companies with sufficient time to migrate existing devices or start fresh as new ones are added to their fleet.
Now is a good time to start planing/migrating Android devices to Android Enterprise (Android for Work)
Android Enteprise Enrolment Guides