If an .ots template that was used as a basis for creating .ods documents is deleted, will these documents be affected in any way? In other words, is it safe to delete templates?
Just try to do it 
Or try a thought experiment: create a file based on a template, send it by email to another continent, and when the recipient confirms receipt, destroy the template. What do you think will happen to your email?
Oh yes, that makes sense. So nothing to worry about.