... but with the dust from the release of Sun&Moon settled a bit (I'm not bothering to put spoiler warnings anywhere by the way) and all the fansites having covered pretty much everything about it by now... albeit hasty, I'll dive right into speculation about the next games.
We could assume that S&M will get follow-up games despite XY having caught us off-guard by not having any. But in addition to the lack of follow-up games in gen6, S&M themselves seem more "finished" and less rushed than X&Y did, so I wouldn't bet on it.
Before we got details about S&M, I was secretly hoping that these games would either function as XY-sequels, despite being a new generation, or that they and XY would get shared sequels after S&M. Turned out there is hardly any connection between the 2 games (with S&M being filled way more with Kanto-references and generation-I fanservice than any besides Gold/Silver-incarnations), and even Zygarde, while finally being given some time in the spotlight with its cell-collecting sidequest spanning throughout the whole game, doesn't even get any actual lore added (there isn't even a mention of Xerneas/Yveltal or Terminal cave or anything)... Sina and Dexio (Sycamores assistants) show up to merely explain the "sidequest", but other than that, they're used to reintroduce mega-evolutions in the post-game, in a rather quick manner as well.
Anyhow, adding the fact that S&M improved the graphical aspect of the overworld quite a bit, as well as essentially getting rid of the grid-like structure of maps, makes the idea of stitching together aged versions of Kalos and Alola go from practical to proposterous.
With SM looking less in need of sequels than XY (sure there is "Necrozma", a mysterious legendary that is clearly somehow connected to Solgaleo and Lunala...but after Zygardes treatment, that doesn't mean much in this regard), it might be safe to assume there won't be more Alola-based games coming in the near future.
3 bases for new games come to mind:
1. Going straight to Generation 8, which wouldn't even seem that strange, if they mean to continue adding "smaller" generations of ~70ish Pokémon (although I personally wish there would be another completely fresh generation like Gen5, especially after 2 generations of nostalgia-pandering...),
2. a return to Kanto. My hope is that most fans look at this option as the least exciting idea for a new Pokémon game ever at this point. Considering we've been to the region in 4 generations, as well as having had the option of returning to its initial incarnation via the virtual-console version of Red/Blue/Yellow (and possibly again if GSC show up on the e-shop as well..), which are even compatible with PokeBank. Add all the constant references and pandering on top of that (from Kanto-starters getting Megas and overshadowing Kalos-starters in their own debut game, to Alola-forms being given exlcusively to Generation-I Pokemon in S&M just now), should make anyone question the reasoning for what might basically be a remake of the first remake. Not even the fact that the story of Gen1 is now more outdated than any other generations story yet again, seems like a valid reason go there. So to this point, I'd say that the only way we are going back to Kanto this generation, is if they do something seriously drastic and refreshing with it. Whether it'd be a "20 years later" fully fleshed-out sequel (which could work as a sequel to Gen2 as well, including Johto in the postgame, and this way at the same time have a Johto-return covered with it already), or such a dramatic reboot, that it would be a different game than the originals.. at which point it's redundant to not just have it be generation 8 anyway.
3. and now to the option everyone would probably have listed first: Sinnoh.
Personally, I love Sinnoh. And that's one of the reasons I'm worried about a "Sinnoh remake". It deserves better than a plain copy&paste+"all the new features added"-treatment, so I hope that these "games" will break the traditional take on remakes we've seen so far in the franchise. Have it be sequels to DPt or some new kind of twist, but not plain remakes with a Platinum-episode smacked on it and a "Battle Frontier Soon"-sign in the post-game...
But alright. Given that these would be Gen7-games, the question is, is there anything pointing towards Sinnoh in S&M?
As far as direct references go, there is the whole backstory about Type:Null, the "ultra beast killer" that was meant to be an artificial version of Arceus, but other than that, there is a crucial thematical connection to DPt:
The core part of the plot of SM is about the mascot legendary being able to open portals to another dimension called the Ultra-world, the home of the newly introduced "Ultra Beasts" of which a handful are released into Alola for the player to hunt down in the post-game.
Dimension being the keyword here. The mascot legendaries of DPt were also powerful creatures that manipulate space and time, and even seem to live in some other dimensions until summoned by Cyrus. The only other time we've ever been to a different dimension in the games before was when we followed Giratina into its lonely home dimension.
The distortion world basically feels like elements from the real world assembled in an unexpected way...
....but the same could also be said for the design of any of the Ultrabeasts. They have recognizable real-world features, but the way they're put together to make a living creature seems abnormal if not downright creepy.
Let's not forget that after the climax of Platinum, Cyrus stays in the distortion world with his motivations unchanged... and after Lusamines bad deeds turning out to be the result of brainwashing by the ultrabeast known as Nihilego, and them even fusing temporarely at one point in the ultra-dimension...who knows what Cyrus could run into.
Oh, and speaking of expanding Sinnoh with things introduced in S&M... Sinnoh forms anyone?
A bunch of random examples that popped into my mind (I limited myself to Sinnohdex, while excluding the PKMN introduced in generation4):
-Ice/Flying Hoothoot-line would make nights in Sinnoh feel a bit colder (it's supposed to be a cold region, yet it has less Ice PKMN than most other regions
-Electric/Ice Raichu as a contrast to Alolan Raichu, while also representing Sinnoh with the type combination
-Dark variations of the annoying pests of Zubats and Tentacools to at least give them a new twist
-Clefairy gaining Psychic since it's closer to the stars on Mt.Coronet than anywhere else. What with Solgaleo/Lunala basically confirming the suspicion of Psychic type being the main type to represent "cosmic"-themes.
-Machop-line gaining a new form so it's not the only original trade-evolution-line that hasn't gotten a new twist yet what with MegaZam/Gengar and Alolan Geodude. Steel to make it an alternative to the overhyped Lucario for the still quite exotic combo.
-Fairy for Ponyta-line to spice up one of the few Fire-types (and Ponyta has always been one of these too bland designs in my view.. also Rapidash is basically a unicorn anyway)
-Poison Quagsire so it fits better with the swamp pokes like Skorupi/Croagunk
-Electric Mantine, because it would be the best that's ever happened to it.
-And Flying Azumarill, because... no idea, I just wanna see more primary Flying types I guess...