What will change?
What will change if the seven Colonies of Benevolence become World Heritage? For the regions it is a step forward. Star status, so to speak. World Heritage status can attract more tourists, business, investors and a larger international network. It is also a sort of guarantee that the sites will be 'protected'.
But World Heritage status will not put the area 'under glass', as it were. These areas are not open-air museums in which nothing can ever change. However, it does mean that their exceptional universal value requires constant vigilance. New developments must be consistent with the character and capacity of the colony in question.