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.
There is the fact that Roaring Moon looks like Mega Salamence. It's Violet Pokedex entry references a "phenomenon" from "a certain region". Usually, other regions are referred to as "far away" regions. But otherwise, this is a fairly strong connection. This region is also the first time we've seen wild Gogoat since Kalos, which makes sense if they're close to each other.
But I do think expecting Kalos is expecting a lot. I just don't see it happening. I think we'd be more likely to get a Pokemon Legends game set in Kalos.
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.
I do agree that the lore makes Area Zero seem like more than it is, but I think that's par for the course for most Pokemon games. The alleged DLC legendaries that we see sketches of, don't make me think we'll see those things, specifically. But maybe ancient versions of the legendary beasts and future versions of the swords of justice. They're explicitly stated to the work of an artist's imagination. But I do wholly expect a DLC pack centered around the third legendary. Something like the Crown Tundra.