I reckon WK will be right, or else it'll end at Nibelheim - the latter just because it would allow them to use what will essentially be a very similar Nibelheim 'map' in both the Kalm flashback and the actual (re)visit. But it would rely on them not expanding too much on what we already have. While Midgar did have a HUGE amount of room for expansion, I'm not so sure the rest of disc one does. Junon was already a pretty long session for a place we end up going back to, and while I'm sure they'll flesh it out a bit for environment sake, I don't see the story being a huge deal longer. Fort Condor will be interesting for sure.
Chocobo stables would be somewhat redundant if we can't catch them in the wild, so I think we should still see some "world map" action on some level... although I can see it being that they just make it so that you ride in maps that exist as FFXII-style corridors between other locations. I'd settle for that, but hope for an FFXV world map combined with enterable cities that don't share the same map, a la original FFVII and Skyrim.
They've also taken some tidbits of the other later game and put them into the remake's part one, so they don't have to go into as much blunt detail later on which might hopefully save some development time. Maybe. Hard to say. But just Kalm, Mines, Fort Condor, Junon feels... too little. At the same time, adding in Costa del Sol, Reactors, North Corel, Gold Saucer, Gongaga, Cosmo Canyon and Nibelheim (re)visit would feel like too much. So in short, I don't have a clue and I can see why they're in this predicament of decision to make. If it's a full priced game again, personally I hope it'll take us further than Junon, but I'm confident no matter what we get, I'll enjoy playing it. I'm excited to see if we get to see Red XIII as a playable character in the future, and how they'll have him move around in a sailor outfit. xD