Physical copies often arrive in stores in advance, and such situations happen. Those who want to play the game "blind" should not read further.
POSSIBLE SPOILERS!
User CentroLeaks on X is publishing data from owners of early copies. Mega Feraligatr, Mega Scolipede, Mega Drampa, Mega Emboar, Mega Scrafty, and Mega Chandelure have been confirmed with screenshots. Also, as in Pokemon Legends: Arceus, a sound is heard when shiny Pokemon (with non-standard coloring) appear, and there are separate icons for them. According to the source, the events of Z-A take place five years after Pokemon X&Y.
At the September Nintendo Direct, Mega Evolutions were announced for Delphox, Greninja, Chesnaught, which were previously unavailable in Pokemon X&Y. According to the official website, the necessary Mega Stones (Greninjite, Delphoxite, Chesnaughtite) can only be obtained through online Ranked Battles Z-A Battle Club, which requires a Nintendo Switch Online subscription and participation in competitive matches.
Pokemon Legends: Z-A will be released on October 16, 2025, on Nintendo Switch and Switch 2.