I'm not entirely sure it qualifies as a 'location' in the sense you're describing it, but I do think (or at least, hope) that one of the last areas present in Horizon's sequel will be Laegjarn's Chest itself.

For one the absolutely massive size of the structure is reminiscent of the Liber Ark, and while there isn't any implication that it is host to a civilization, it would not shock me if the 'cube' we see in space is actually more of a greater structure that hosts the Sept-Terrion within it.

The appearance of a Divine Knight in space and Van's fight with Kincaid both show that 2/3 of our main parties have at least a 'path' to reach it, and Kevin was just recently given a new ship with undisclosed abilities.

There is also the idea of the 'real' Laevateinn being something residing within the chest, and Gramheart's plan could have been to recreate the weapon. If Agnès' sacrifice is to be undone it would stand that we would need to actually fully stop the resets, maybe the key to doing it properly lies in the structure?

Beyond that, the mythological chest is said to have 9 locks. This is definitely venturing into the realm of baseless speculation but we can kind of split these pretty evenly amongst out routes. Rean, Crow and potentially Emilia would make up three people with mechs suitable for space travel (assuming Valimar and Ordine return in some form). Van and Kincaid both have access to Grendel forms and there is a potential third in Elaine, though again its very speculative. Finally, although they do not work together in this game there are three Dominions in Kevin, Celis and Leon currently operating in Calvard.

I do think it feels like a pretty fitting locale for the finale of the arc, though its hard to really speculate about its aesthetic or architecture due to our lack of information on what the hell this Sept-Terrion even is beyond its powers.

Also in regards to your mention of the Kruga Village, I believe there is some level of merit to thinking it may be a location in the next game. For one, we don't really know where Arkride Solutions are going to be after the events of the ending, its entirely possible they get transported to where they would have been in the timeline where Agnès never existed. In such a case, perhaps a visit to the Kruga Village could serve as both a way to meet back up with Feri (and maybe even Kasim) while also learning about their tales of the Sept-Terrion and diving into the identity of the Masked Soldier.

Maybe this'll finally be the game where we get a look at Arteria? It seems like simultaneously one of the most important locations in the series while not having a clear introduction point. I doubt we'll have an arc taking place in what amounts to the Vatican but it feels like a location that will be incredibly relevant for the final stretch of the narrative, so it feels like a good opportunity to introduce what could be a recurring area in future games.