Reminder that Z/next Gen 6 game will be announced next month, with the Zygarde Formes, Ash-Greninja and a plot related to the movie.
That's a rumor until it's confirm on Serebii website or Pokémon youtube channel.
I dont even know how you could call that a rumour. A rumour usually means someone on the inside has told this guy who told this guy who told this guy etc
This is just an estimate.
Not to mention that both previous mythicals had alternate forms coded to events present in ORAS. Datamining shows that there's no such thing for Volcanion, meaning that in the very likely even it also has a mega/alternate form, it's going to be in a new game. Same for the Zygarde forms, its two unreleased signature moves, AZ's Floette and its own signature move and possibly Ash Greninja due to having a special animation in Tretta coupled with the fact that Tretta animations are taken from the main games.
How? It's literally just a mega evolution. Just Ash can use it without any stones because their love is super OP. Writing about the love is the best writing fucker. You're just jealous you don't have a Pokemon to love.