LogFAQs > #979070960

I don't think it's in the past. What little the trailer showed off included modern clothes and outdoor furniture styles. I'm thinking it's taking place after X/Y.

Other predictions:

• It's keeping the Kalos starters instead of a new mix, but this time they have Mega Evolutions.
• Instead of focusing on regional variants and evos like Arceus, it's mostly gonna feature new Mega Evolutions (perhaps primarily for Kalos Pokemon.
• Set almost entirely inside a giant Lumiose City, with maybe the outskirts or possible Hoopa shenanigans to smaller sub-areas.
• As a result, will not really play all the similar to Arceus.
• The A in Legends: Z-A is for a new legendary.

If it's early 2025, then it's still only the same 3-year dev cycle from Arceus to Z-A, so I'm not gonna get too excited about the idea of Game Freak "giving time to cook".