Midgar is the shortest part of the game & basically a linear tutorial, the world map, towns, Junon, Ocean floor, Wutai, Fort Condor, various dungeons, smaller areas like dig site etc & of course Golden Saucer is going to be the most ambitious work Square has ever done, once or if fully completed, it will make FFXV's world map look like a fucking demo.I don't think them adding new stuff would mean that the game could potentially never come out.
When the game releases, it'll have been less than three years since SE took the game over from CC2 and turned to internal development. I just think within this time, they were able to focus on the original Midgar and polish the hell out of that while adding bits to the story. Less than three years is not a lot of time to make a more ambitious Midgar.
While that's fine, when they split the game into parts and Midgar became its own game, expectations were raised as to what they would do for each part.
No one should be surprised at cuts or Part 2 being delayed until 2023/24.
Oh, Part 3 will have to expand on Midgar again too, though i expect by that point they will just reuse assets.