I would update the old templat
Add a rule on Open which checks the contents. Select a field that would be blank a new form but not on an existing form. Set the rule field is blank, action display message "do not use this old form, blah blah, etc"
Then the next action is open a form and open up the new form for them, then close this form.
You could just close the form and make them go open the new one themselves if you really want them to learn. :)