Update: Zeraora is not available in Pokemon Shuffle.
Original answer: We don't know if GS (Genius Sorority, the game's developer) is going to include any of the new Pokemon in USUM. The game is currently in the middle of a 24-week rotation of events, in which all event Pokemon are catchable. The end of the first 24 week rotation was 2 weeks ago, and the game looped back to the first week of the 24-week rotation, implying that GS is done adding new content and automating it. Dataminers have found that the cycle is supposedly going to continue until 2037.
Source: I'm an end-game player of Shuffle, and have pretty much completed the game.
List of Pokémon by Pokémon Shuffle list number (Bulbapedia)
