I highly doubt this is the case, but...

What are the odds this whole thing is taking place in the Spirit World? Like whatever happened wrecked the human world so much that everyone, human and spirit, retreated into the Spirit portals to stay there forever?

idk, could be cool. Just something I thought about. And I know that's hard to believe given we haven't seen any spirits in the trailer, but that's odd even if it's taking place in the human world, so it could be the case.