Gigantamax and Dynamax are fully related to Distortion World as I've stated before.
XY featured MEGA for the first time to later on release ORAS pointing at Rayquaza as the first ever MegaEvolved Pokémon.

Cyrus' far from being done.
Game Freak about to revamp
Diamond and Pearl introducing
elements from it first in Galar.

Fenrir, the chains that bind him and whose release will be the beginning of Ragnarök.