I think these games will have an interesting way of doing things. They could have easily gone back to the drawing board and come out with a 3rd version "Eclipse/Stars", but they didn't. Despite disagreements between translations, I think that it could be an alternate universe like what was said in the video. A couple of my thoughts:
- I think there will be Gyms and the League fully established in this reality of Alola, with the Trial Captains as Gym Leaders and the Kahunas as the E4. Since there's only 7 Trial Captains, I think it would be an interesting call back to Gen 1's Giovanni to have Guzma as the 8th. IIRC, he was wanting to be a Bug-type Trial Captain. I also vaguely remember him being opposed to the Pokemon League taking place of the Trials, so maybe that could come into play for how Team Skull operates in these games.
- Despite Gyms, I think there will still be an element to the original Trials thrown into the mix. Maybe after defeating the Gyms of an island, you have to battle that island's Totem.
- Instead of true fusions like the Kyurem forms, I think this looks more like Necrozma possessing Solgaleo and Lunala instead of fusing with it. It's hard for me to explain, but it looks to me like some sort of parasitic armor. It's really interesting because it's not a UB but yet it's hinted that Solgaleo and Lunala are. Another interesting thing is that its Pokedex entry says it has a vicious disposition, so maybe Necrozma could be the first Pokemon main antagonist like how Lusamine was the first female main antagonist. I think that the whole story behind the UB's will be explored, these games are after all called "ultra".
- Speaking of Lusamine, what if the roles of her and her husband Mohn in the story are switched, with an added twist? Mohn is the head of the Aether Foundation and actually seeks to destroy the UB's because one was supposedly the cause of Lusamine's disappearance, thinking shes actually dead, possibly because of Necrozma directly or indirectly. You end up finding her later in the climax, and it has something to do with Necrozma taking over the Legendary.