What happens if I delete a user template?

If you delete a template that has been assigned to users, the users will keep the last known settings they were given by the template.

If a user template gets deleted from PBXAdmin, the users will keep the last known settings they were given by the template. 

Changes to a template, do not effect users who have been assigned the template. Every time you want to release a new version of a template, you will have to assign users again, and release the template.