I think the decision of making more packs beyond 2022 will depend on the profitability/success of the game in the 1st semester of 2022. That's why I think they'll go strong for the next packs, and probably one of them will be an Aviary pack. If PZ keeps selling well and having activity, we might get 2 further packs in 2023, but not much more.
My prediction is:
2022
Q1: Aviary pack (8 flying birds + 2 ground-dwelling birds)
Q2: Scenery pack (4+1 + 1 flying bird in exchange of 50-100 building pieces)
Q3: Animal pack (7+1)
Q4: Scenery pack (4+1 + 1 flying bird in exchange of 50-100 building pieces)
2023
Q1: Animal pack (7+1)
Q2: Animal pack (7+1)
Honestly, with how good the new pieces of the last two packs were, I don't really know if I'd be willing to sacrifice 50-100 pieces for another bird

What I would be willing to sacrifice is an exhibit animal for a bird, and the fact that there are a hell of a lot of birds that only vary very slightly from each other, I think it's possible to do it within the same budget of a exhibit animal.
For instance, if they use a base model/base pieces flow for their animal creation, once a scarlet macaw is made it is probably possible to then make a blue and yellow macaw within the budget of an exhibit animal. Sure, people would say it's a clone/reskin, but when it comes to birds having a bunch of "variants" is inevitable.
I’ve read on other posts that there is rumored to be capybara, lord Howe insect, buoys and on one post I sow someone say “flocking behavior” or something like that.
A lot of it was found using datamining and all of it had tags that referred to older packs/themes (capybara sign referred had the aquatics pack tag, howe insect had australia tag, japanese pieces had the ingame east asia tag) so it is most likely just scrapped content from older packs. There was also an emperor penguin sign tag that someone found during the beta and later on it turned out that we got a King Penguin instead. Not that that automatically means that a capybara will never come to the game, it is the most requested animal at this point and Frontier seems to take the meta wishlist into account; but it just doesn't mean that we'll get one in the next pack or so.
The flocking behavior was a bunch of tags that are also present in the PlanCo files, so just leftovers from that game.
There's essentially nothing in terms of leaks to go on to predict the next pack
