The more I think about it, the more I think it must be connected to something ARR players can get to, not just because of issues with FC people not having access like you pointed out, but also personal houses not being able to show it off to friends who don't have the expansion and that'll just cause annoyance.

History has shown us that SE likes to repurpose things (which I can understand it is more efficient use of their time) so I suspect we'll literally get 12 more wards and subdivisions at the new area, exactly the same design as we have now (but obviously a slightly different layout). So that'd be 24 wards and if it's 30 houses per ward like it is now, that'd be another 720 houses per server... doesn't sound so much now :S Maybe they'll increase the total wards overall, although I'm not holding out much hope of that...

From what I understand the reason they can't just keep expanding the existing wards are because each ward are a separate instance that always have to be running (like a normal zone) so with 72 instances per server and 64 servers, that's 4,608 zones constantly having to run. Although I think they're going to have the same issues with 4.0 (assuming they do it the same way), 24 new wards (12x2) over 64 servers is still another 1,536 zones/instances, but they likely have some budget in 4.0 for new hardware for just this.