Of course most of what I submitted as "substance" is somewhat flimsy, and by all means I'd much rather have SM sequels than DP remakes at this point. As flimsy as "Niji", the Strange Souvenir and palm trees pointing to Hawaii at first glance, because remember just how many naysayers there were when that was brought up, or that a backwards flowing river could in fact be in reference to one found in a Hawaiian region and not specifically just limited to the Distortion World?
Not quite so sure why some thought those were my own arguments as opposed to myself playing devil's advocate, which has to be the case when some are dealing in absolute terms when it comes to possibilities, which at this point is all that any future entries are, as reliable, or unreliable, we may find the source of the rumour to be. To simply write off any potential possibility simply because it doesn't outright go out of its way to confirm that it is certainly the case would be naive, though, and especially with how recent games such as XYORAS have gone out of their way to hint in a similar fashion, though perhaps a little more on the nose in hindsight. To simply say that these arguments don't have a definitive conclusion is very much backwards, considering that the point of a hint is to not give a definitive conclusion but to rather tease a possibility. I'm not saying DP remakes are next, or even this generation, I'm simply pointing out that it gives an argument for them more credence than "oh, they're next in line for remakes and that's that".
As for the Ultra Beasts and Necrozma? The Ultra Beasts, I thought, was pretty obvious: portals leading to another dimension in a similar fashion to that which led us to the Distortion World, and a focus on some larger mythos - aliens as opposed to Gods. As for Necrozma, that's a little bit more difficult to explain, but alas, I'll try to do it here regardless: Necrozma, the Prism Pokémon, is known to refract light and is very likely a reference to black holes, which also absorb and refract light (probably also a reference to Newton's prism experiment, but besides the point). In reality, it is known that the fundamentals of physics - space and time - break down around black holes and perhaps, it is though, to a lesser extent, wormholes. As we know from the Dimensional Research Lab, space-time in Alola is being used to located Ultra Wormholes and other disturbances (as a side note, them being situated next to a building which houses Aether on the top floor seems a lot more fishy now, right?). As a little add-on, I must add, it was pointed out on many occasions during Null's reveal that it's head gear which limits its power is a reminded of a similar symbol found on Arceus. Now, we know that Null - due to its friendship with Gladion - removes this head gear and masters it's power. What are the odds, then, that Arceus is also going to lose the ring and unleash a greater power in a future game? Because I'd say as a nod, that makes it fairly likely.