Great post, also made me notice something I didn't saw before, so its always good to revisit old information. In the festival video, at 1:04 you can hear a cry of a Pokémon and see the blond girl's bag shaking. She has a Pokémon inside her bag, but i can't identify the cry tho :s
I'd like to point out that the battle royal video also probably revealed the protagonist's cannon names, Elio and Selene. Well, one of those isn't 2 letters off of last gen's heroes.
They are likely placeholder names, with the canonical names likely not getting revealed until after the games are released. Some previous examples were Hilbert and Hilda (BW protagonists) once named Blair and Whitlea, while we also had Calem and Serena (XY protagonists) shown with the placeholder names Xavier and Yvonne, with the canonical names officially revealed due to the fact the one not chosen as the player gets an in-game role as the main rival.
There's been nothing hinting towards the opposite-gendered SM protagonist being a rival, since Hau appears to be the only rival in this game so the other thing I can see is the other protagonist being an NPC partner in the battle facility which will then likely reveal their canonical name, similar to Hilbert/Hilda who acted as the NPC partner in the Battle Subway but didn't appear in the game outside of that.
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A few interesting points brought up that I'd forgot about from E3. The mysterious sound from Lillie's bag most definitely seems like an important Pokemon, though it would have to be a smaller Pokemon given the size. It's odd that if it is a Pokemon that it presumably isn't in a Pokeball? Either way I think this just adds to the mystery surrounding Lillie, one of the many things I'm looking forward to uncovering in S/M!
The Pokemon cry from inside Lillie's bag almost sounded like a Skitty to me, but I can't be too sure. It's certainly small enough to fit inside a bag like that, and I can just invision her having a Skitty while Professor Kukui has a Rockruff.