Hey Teebs, I'm not surprised that your sources are dry up right now, if there are plans of expansion, the fact that ANY information has leaked this early is probably pissing off the crap out of UO
But again those surveys were a clear indication of their intentions.
But I've said it before, I can understand how all of LC could be taken over and replaced, but I'm going to stick to my guns here and say only the arabian sections gets taken over. There is nothing in the Potter books remotely close to a site down restaurant, and to make two self service restaurants in the same area would be befuddling, especially if they pretty much serve the same food.
Logic leans towards the expansion of WW into the arabian section, and leaving the current arch in place there that leads from the PF and Mythos part to the arabian.
My theory for the transtion from Diagon Alley TO Hogsmeade's current gate would be a tunnel/fireplace, with smoke and mist and lights that you walk through (the Floo Network) and there you go.
If not, its a magical world, they can imagine something and bring it to life, because its "magic" and its a theme park