My two (or three) cents:
So far the pictures shared by Planet Zoo don't show any new building pieces and/or foliage. But what it does show is that the map was specifically created to show-case the update, and likely, the future DLC (and it's not a pre-alpha, early development build, since it includes foliage from, at least, the Australia Pack). Potentially it's the new (or part of) the "timed challenge scenario" that comes with the DLC.
Everything hints towards Asia (leaked sun bear, very asian theme in the Billboard and update posts, Orangutan statue, diving for gharials...). They won't use SouthEast Asia for marketing purposes (it's too long).
Anyway, I think this will be a DLC focused on animals rather than foliage and building pieces. So we might see more animals, but less new building and foliage. And I think that's how Frontier will continue, with Europe, Birds, North America (don't know in which order exactly) and the final one, closing the game, Africa (Summer 2022), with meerkats, rhinos, leopard,... and that's about it. And no TMTK, of course.