Pokemon X & Y's fabled follow-up Pokemon Z was apparently planned all along, as an alleged leaked design document hints at an alternate form for its likely Legendary mascot

gamesradar.com:

Pokemon Z apparently was planned to exist once upon a time, according to an alleged document from the enormous Game Freak leak.

Pokemon Z is the RPG that everyone thought was the next, inevitable step for Pokemon after the release of X and Y, and to this day, it's still a bit of a mystery why it never happened. Even now, more than 11 years on from our first steps into the Kalos region, X and Y are the only main-series duo of Pokemon games – not counting remakes – to never receive either an improved third version (like Emerald and Platinum), sequel (like Black and White 2), or DLC (like in Scarlet and Violet). For fans of the Kalos region, that makes the upcoming release of Pokemon Legends: Z-A all the more exciting, but it's now been claimed that the 'original' Pokemon Z was once supposed to happen, too.

An alleged design document for the Kalos-region Legendary Pokemon Zygarde has now apparently been uncovered from the Game Freak leak, and when translated (via Google and DeepL), it makes reference to the Pokemon's different forms, and notably mentions it changing to a different form in the Z version. That would certainly imply that plans were in place for the game to happen, but nothing else is mentioned about it here.

If this document is real, there's nothing on it to indicate how old it is, and with that in mind, it could be that the Zygarde Complete Forme added in Pokemon Sun and Moon is the alternate form it refers to. Sun and Moon also introduced the concept of Zygarde Cores, Cells, and its 10% Forme, and it always felt slightly odd that all that happened in a region that the Pokemon wasn't introduced in. Of course, it's better than not having those forms at all, and if it's to be believed that Pokemon Z ended up being scrapped, then perhaps the developers just thought it was best to bring Zygarde back for the Alola region, instead.

As with the other supposedly leaked information from the Game Freak leak, do take this with a pinch of salt – especially now we're