How the rest will be divided up (my theory)

[JJ Strife]

i dont expect it to be open world, at all, that would really surprise me

Possibly yes. But even if it's not a complete FFXV style open world, I think they still need to go with fairly large open areas in order to convey the scale of the world. Their next best option would be kind of segmented semi-open areas, a bit like how the later Souls games work. I'm thinking Bloodborne and Dark Souls 3 especially. DQ11 had a similar approach too (but had more loading screens that the Souls games). Any of those approaches would work fine too.

Even with that style though, they still have a situation where the sheer size of the world needs to be represented to scale in some way, because it otherwise wouldn't feel correct in terms of the lore of the world. Like for example, Midgar and Junon need to feel a long way apart. Because why would Shinra (or anyone) build 2 cities that are just a 10 minute walk from one another. That wouldn't make sense. You'd just join them together if that was the situation.

I think there’s just enough stuff there to put the rest of disc one in part 2, and then part 3 could be the rest of the game. Your four-part plan seems to be pretty possible too, though.

The rest of disc one contains most of the entire world map though. Pretty much everything except Mideel and the Northern continent (guess they could push Wutai off into the game after). How could they possibly manage that without heavily limiting every other area they create?

They would basically have to create places like Junon so they're just as brief as in the original game. Like you're only in the upper city part of Junon for 20 minutes or something. I just can't imagine them doing that after how big Midgar was. It would kill the sense of consistency in the world design, and would undermine that whole reason why they chose to split it up in the first place.

I guess it's not impossible, but I really hope they don't do that. I want places like Junon to be huge towns that you can explore for an hour or so. Not as big as Midgar obviously, but at least made with similar sense of scale and detail in mind.