I would like a return to Kanto where we can see the continuation of Lillie and Lusamine's adventure.
SM had a lot of references to Kanto. Every set of games has references to previous regions, but there tend to be more references to the next region getting a remake than any other, plus data for Pokemon from those regions found in the games. Ex: Hoenn had references to both Kanto and Johto, but a lot more to Kanto. The day and night cycle from Johto was done away with until DPPt, and although Emerald came after FRLG, I still think it's interesting how Emerald removed all references of Johto from the original RS. For Pokemon data, Diamond and Pearl had Johto starter data, and XY had Mega Latias and Latios in the code, while none of those were obtainable in the games. SM has Mew's Z move, while Mew isn't obtainable in SM, and I'm not sure the z crystal can be obtained legitimately either. It could be said not to expect Mew to be like them since Mew has always only been event obtainable, but Deoxys lost that status in ORAS.
Going back to references, there are a ton of Kanto references in SM.
1. The player character and mom are originally from Kanto
2. Professor Kukui battled the Kanto Gym Leaders and E4
3. All of the Alolan forms are of Gen 1 Pokemon
4. The Nugget Bridge mimics at Malie Garden. The last one also mentions wondering what Giovanni is up to these days.
5. Oak has a cousin studying the regional variants/Alolan forms
6. Kanto and Johto were mentioned as influencing certain cities in Alola. IIRC, Heahea City and Malie City were both mentioned to have been formed from travelers from those regions.
Additionally, there were two sets of starters to receive Mega Evolutions in Gen 6: Kanto and Hoenn. Mega Blaziken was shown first in XY, then the other two came in ORAS. I don't really think it's likely there'll be more megas in the future, since from what I've heard a bunch of mega stones aren't even obtainable in SM and I read an article about some needing to be earned from online play? I think the mechanic may continue to exist, but that there probably isn't any interest in making more or having it being near as important as it was in Gen 6. (I also think if there's a gen 8, z moves will get similar treatment from then on)
Additionally, we know nothing of Necrozma's mysterious connection to Ultra Beasts. It just had a random appearance at the end of the postgame UB quest, and appeared in Ten Carat Hill's grass like a regular wild encounter (and just like the UBs). We didn't get much info on Zygarde in Kalos, and while some people including me were expecting Z, it was actually in SM, a completely new region, that Zygarde got backstory, instead of in a third version or sequel. Maybe that will continue with Necrozma, where through Lusamine we could learn more about it in Kanto games. I don't really think it'd be good to just leave the connection unexplained.
In the anime, Ash travels with a lot of the female protagonists. There was May, Dawn, and Serena. Leaf didn't exist yet when the anime was in the first season, and Unova seems to be an exception to many common themes in the series in more ways than one. I don't watch the anime and consider it a separate universe from the games, but I wouldn't be surprised if they had some extra/future game knowledge, considering some Pokemon have appeared way ahead of their official reveals.
Even if all this can be countered, I still just want to see Lusamine make a recovery ^~^