I don't see them making the firehouse, this will likely be a one off item unless it sells really well like the Minecraft lego did (an early Cuusso project)
Lego do a range of buildings know as the modular series. Nice retailed old style buildings. These range from £100 - £150. Something like that would suit it well. Of course there is the licensing fee. The new simpsons house is £180. Of course all of those come with figures and some of them include veihcles.
There was the Batman Arkham Asylum, which was £130. Didn't have much to the actual building really. Was just the front of the building with some stuff going on behind it, but did include a van. Maybe that could be a cheaper option. But again, I don't see it happening sadly.
I do hope they make it so you can change between the two different version, like they did with the Delorean. It makes good business sense as for the minimal cost of a few extra brick and stickers, some people will end up buying extra sets, which is probably why they did it with the BTTF set.
I am very excited about this, bit of a Lego collector and this is the set i've always wanted!!!