Given that no one actually has any experience with this in 2.0, I will say that, assuming they stick to their normal billing practices, if you do not cancel before your renew date it will automatically charge you and give you another month of access. If you do cancel before your renew date you will not be deleted. In addition, your characters will stay there until you return, will probably hang out for a couple of years without incident, and, if they do disappear, will be able to be reactivated by SE customer service (once they are actually available to do things again).