Either scottish highlands or a town of some sort, the town would fit with their theme that they seem to have going with going out on the town and partying. The weird looking kilt in Dream Home Decorator (the utility-kilt) could have been a hint for Scottish Highlands as well.
I'm just skeptical about them making the scottish highlands in the sims4 engine though, they don't do mountains and hills very well in the sims4 engine, the worlds often feel pretty flat, and I hope that if they do make the scottish highlands that they will have fog and detail so that it doesn't just look like willow creek with a few castles.
