What are the chances of bradycardia returning?

Depends on the cause: If due to inherent dysfunction of the electrical system, it is a safe bet it will come back at some point down the road. (however, this can often flicker on and off with normal intervals of many months in between.) if caused by a reversible process, e.g. Very high potassium in the blood or very low thyroid function, then it probably won't return as long as that cause is prevented from recurring.

100%: Bradycardia just means "heart rate <60". It will return in all human beings at some point, guaranteed; generally every night for most folks. Nothing wrong with that!