I have been banned 3 times now (11 accounts total). My RMAH/Mule account has survived all 3. I leveled 3 toons to 60 with DB, traded items/gold everyday, and even accidentally ran champ farming on it a few weeks ago. So I would say its less likely to get banned if you haven't botted on it. There is no yes or no answer, some people's mains have been banned, but majority have not. In the end blizzard can do as they wish. But there really is no other option than to store on a mule account, so just do it.