I'm good with USM. I'm thinking along the lines of what we call Black 2 & White 2, many refer to it as BW2 so Ultra Sun & Ultra Moon should have something similar. Keep it simple.
Anyway I re-watched the USM debut trailer/sneak peak and though to quickly comment on somethings:
Player's Room: I noticed something that looked different about so checking back I figured it out: in place of a Pikachu Doll there's a drawing of something. Can't tell what it is but it's an odd change to make. Now I'm not saying it's going to have major impact in the story, but I'm curious why the change and if maybe the picture either tells us something about the playable character or if its going to foreshadow something.
Route 1: Aside the path leading up to Iki Town having bloomed with more colorful flowers on the bushes, the player's house has the garage open (revealing a car parked inside, which I'm kind of surprised as where are we going to drive it?) and there's a surfboard leaning on the side of the garage (who owns that? Mom? Doesn't seem like asurfer, than again how enthusiastic she is about Alola guess it wouldn't be surprising to hear she can/tried to learn to surf. Or maybe something of dad's? Ooh, that would be a twist! Instead of of our mom it's our dad who we moved with to Alola (or maybe actually give us an entire family unit this time around)!).
Pikachu Haven: Hmm, I noticed there's a Trial Guide nearby so maybe this is for a new trial? Thinking about it, considering that your only a Trial Captain until your 20 its an ever-changing position so maybe we may have a whole new slew of Trial Captains. Course if they did that they would probably be types not used before (unless this is a Psychic-type trial and just messing with expectations). Though there's still that Gym factor hanging around.
Togedemaru: Totem Pokemon? Though it's not glowing, so what else could it be? Start of a Gym Battle? That would be a neat battle transition.
Mimikyu & Lycanroc (Midday Form): Probably new Z-Moves. Hopefully they don't forget Lycanroc Midnight Form (wonder if they'll share the same Z-Crystal like the Tapu).
N-Solgaleo Stomp: Hmm, when N-Solgaleo stomped its foot it looked like it was at the alter (before switching to showing us it in Ten Carat Hill background). So will this transformation/fusion/armoring up be done at the alter?
Z-Twist: A few things about the Z-Ring scene. One, the Z-Ring is now different. Where it was mainly white before, now its mainly black. Only part that remained white was the top triangle/arrow and the "Z" symbol. Second and probably more important, the Z-Crystal in there is like no other Z-Crystal. What Z-Crystal is it. Third and finally, you twist to activate it. Is it just for that Z-Crystal, or is that how you activate all Z-Crystals now (which I would much prefer as the poses looked silly).