I'm still holding out hope that Frontier's original plan was for three years of support, with 4 dlc each year, for a total of 12. (The wikipedia page for Planet Coaster lists 12 major packs/updates, so it doesn't seem completely unreasonable that they might have had a similar plan for PZ -- despite being very different games). I'm hoping they continue with that 12-pack plan, even if covid pushed the dates back a bit.
I'm not expecting anything, but at the moment, my hope is for:
1. Arctic Pack
2. South American Pack
3. Australian Pack
4. Aquatic Pack
5. South East Asia Pack
6. African Pack
7. North American Pack
8. Aviaries Pack
9. European Pack
10. Nocturnal Pack
11. Tropics Pack
12. Endangered Species Pack (or Fan Favorite Pack).
Each of these last three packs is broad enough, and non-repetitive enough, to keep my hopes up for many animals that we haven't seen yet. Similar to how Planet Coaster threw in more coasters as it approached the end.
The Nocturnal Pack could introduce new lighting elements for the builders, and has long been my internal justification for why I think they have chosen to hold back some popular animals like the leopard, capybara, tasmanian devil. platypus, porcupine, armadillo, ocelot, red fox, raccoon, coyote, cougar, additional hyenas, etc.
The tropics pack is in some ways a companion to the arctic pack. And since the "tropics" includes deserts, islands, jungles, and rainforests, it's a broad enough category that they can throw in a wide range of animals. (I'm assuming the European and North American packs will give us many temperate animals, although there are obviously other biomes there too).
I go back and forth about whether I'd prefer Endangered Species or Fan Favorite for the final one. Mostly depending on which animals I'd like to see that haven't been accounted for yet, and who I trust to choose more of them on any given day -- the devs or the unruly crowd!
Needless to say, I'd love it if the game went on even longer than that! If they decided to go for five years instead, I think they could easily go over every continent again, plus several areas like East Asia, Madagascar, Oceania, etc that haven't really been covered, and dedicated packs for biomes (desert, tropical, temperate, mountains, etc.). I'd also love to see petting zoo and exhibit animal packs, as well as aquariums and marine animals too. But I've limited myself to these 12 for fun prediction purposes.