I was thinking about this yesterday and Universal has a unique opportunity on their hands. They are building Harry Potter rides, shops, etc. but the way to access those is through "London" and specifically Diagon Alley. This means they will have a modern "London" area, not a Harry Potter area, that guests walk through unless they specifically desire to enter Diagon Alley. If I was building this area, I would leave that on the table as a non-HP zone that can be used for other events, such as HHN.