The thing is, the third legendary and the rumored Scarlet and Violet DLC legendaries pretty much confirm that the Time Machine isn’t actually a Time Machine. I don’t want to get into narrative specifics, but the supplemental lore pretty much states that there are more dangerous parts of Area Zero that we have yet to explore, and that there is a reason we don’t actually get a glimpse into the past or future that these machines access.
We haven’t gained access to a part of another region since Gen 2, so I highly doubt that we’ll see a return to Kalos, or even a part of it- if you look at that part of the map, it’s tall and featureless, and would probably be pretty lame exploratory content. Even if we returned to Kalos in some format, it seems to conflict with the nature of Scarlet and Violet’s narrative and thematic concepts, unless we’re just considering “stones” (mega and tera) to be the connective tissue. I think the best we can hope for is maybe a small, island-sized open world similar in structure to Paldea, but I do think that Game Freak is going to experiment with the DLC model to see what works well for them. Sword and Shield was expanding on the idea of the Wild Zone, which was ultimately a failure, so I would assume Scarlet and Violet would expand on the open world concept.
But hey, I’m a person who likes to make connections and attempt to tie things together logically, and Game Freak has proven to very-much not-be that. So who knows?