It's not possible currently but certainly a consideration for future versions.
In the meantime you could modify the code to upgrade somebody to an 'Expert', 'Editor' or 'Moderator' based on their points. All changes to a user's points go through function qa_db_points_update_ifuser(...) in qa-db-points.php, so at the end of that function you could run a little DB query which sets the user's level in qa_users based on their points in qa_userpoints (taking care not to mess up admins and the like!)