I work in the translation and localization sector of Nintendo of America, and I am, as of writing this, working on a trailer for USUM that will be released on August 17th(that's the plan, anyway). I have decided to leak some information anonymously so that people will stop complaining about the game not being seen anywhere.

Some things that are in the trailer:

-Gyms will be in the game. In order to challenge a gym, you must first complete the trial for the Leader/Trial Captain. The trailer shows Ilima as a Normal-type leader and the Totem is now Raticate(Alolan) in US and Gumshoos in UM.

-There will be a new Lycanroc Form, Twilight Form. It evolves by being traded from US to UM or vice versa.

-New Alola Forms for Gen 1 AND Gen 2 Pokémon: Politoed is now Water/Fairy and has lilypads Incorporated into its design. Its Ability is Flower Veil. Dodrio is Flying/Fighting and has Scrappy, and has thicker necks, different coloration, and teeth. Onix and Steelix are both Ice/Ground and look like the Crystal Onix but with clumps of dirt sticking out. Dunsparce is Fairy/Dragon, and its Ability is Intimidate. It has big fangs and permanently angry eyes, with the blue areas now red.

-Hau and Lillie are almost the same, but Lillie wears her second outfit from the start and is more outgoing. Hau has a new outfit too, with longer, dark green shorts and the same shirt with the colors reversed. Hala is still a kahuna, but the title is now just a title, and Grand Trials no longer exist.

-More Z-Crystals are received from side characters, like Kahili meeting you at Hano Grand Resort and giving you Flyinium Z.

-Togedemaru and Mimikyu are shown to have exclusive Z-Moves(the animation from the first trailer), but no mention of Lycanroc.

-The trailer ends with a promise of more to come, with the same twisting Z-Ring animation, as well as Sina showing off the Mega Ring at the Tide Song Hotel, and shots of Solgaleo and Lunala in their new forms preparing to use a move.

The end.