After GGG more than likely KOs Jacobs the regular belt becomes vacant. It doesn't go to GGG because he is already the full undisputed WBA super champion and doesn't need that belt.
It is my understanding that when GGG wins (and he will, Jacobs did not want this fight now) Jacobs's title will become vacant and the cycle will start over, with someone else becoming WBA regular world champion in the near future. If a sanctioning body is given the opportunity to do something sensible, you better believe they won't take it
Fuc all the GGG haters on here. GGG is fighting the best middleweight in the world next to himself. You can all shut the fuc up and quit your b*tching and crying now although you surely won't do that. You will find something else to trash GGG about or predict that Jacobs will beat him. You had better pray for a Jacobs win because if GGG beats Jacobs that will make the 2nd middleweight champion he has defeated. It will be very hard for you to say he never beat any good fighters then but I'm sure you will try.