I understand the poor Justin is quite busy at the moment 
-Greg
Your assumption is basically right, it's how we store it in the DB with the appropriate metadata to make it v2. If you have a completely "valid" v1.0 template, then you will see absolutely no changes to your code when you click "Edit Draft" with Email 2.0 enabled. It will just suddenly be a v2.0 template if you approve it. However, what you'll see about the v1.0 Email Templates is that even just having the following is considered valid:
<div class="mktEditable"
Literally, without closing anything. In the old Email Editor 1.0, we would run HTML Tidy on that prior to creating a new email and the resulting code in an individual email using that template would obviously include much more. So, when you click "Edit Draft" with Email 2.0 enabled, we're also going to run that same HTML Tidy validation so that the resulting code of your template has all that stuff in it. This is how we'll ensure that if you have a v1.0 template, that when you approve it as a v2.0, it will cause your individual emails to look the same.
Make sense?
Justin