You can define your own permissions for the Drupal permissions page (/admin/people/permissions in modern Drupal, Drupal 8, 9, 10, and beyond) and then add conditional options to your code to do different things based on the role of the user and the permissions configured by a site administrator. See how!
Drupal 7 has a much longer lifespan than the (already pushed back) official date, and Drupal 8 has an essentially infinite lifespan because it can update in-place to Drupal 9 easily and the same will be true of Drupal 10, 11, ∞. There's no reason to rush an upgrade— but there's no reason to wait either.
How to keep modules compatible with Drupal 8.7 and below while still using the new services.