Its hard for me the answer without being able to do a full diagnosis but I would say any abscess should be taken care of sooner than later. Even if its draining, there is a constant infection present. If the fistula closes, it can spread rapidly to other parts of the mouth, face, neck region, etc.
So is your dentist recommending to extract the tooth and place a bone graft in? I'm not what the success rate of a bone graft is when there's an infection in the socket.