Well it seems things are seperated. It's sad I think. Feels so outdated and it breaks immersion. Especially with houses, but also a lot with dungeons.
Red Dead Redemption had no seperation of interior/exterior cells

I'm hoping for at least open cities though.
If the engine isn't capable of handling that many objects, then perhaps it's not as good as everyone thinks it is (if that's now the case).
But... wouldn't it be possible to have some really advanced script tied to an object distance? So that, whenever you're not seeing something, it isn't rendered within the "object-view-distance"?
If that's possible, it would allow us not only to get rid of any loading screens, but also improve performance in general?
Then again, this is just a theory I have and I know nothing about scripts