I think I’ll expand my answer (I had only listed what I think are the most requested species) because I’ve been thinking about this a lot... there’s animals I hope will be prioritized in future DLC, even if they never add aviaries and such:
Would love a “Central America” pack so we could have sloths, and maybe the capybara, Scarlet ibis, puma, or howler monkey.
Definitely want meerkats in Africa pack... I also love red river hogs, fennec foxes, fossa, and giant elands. And I appreciate so many of those big African birds.
if we wouldn’t get a puma in Central America, then hopefully in North America. I’d also love Moose, Roosevelt Elk, River Otter, Alligator Snapping turtle, Lynx, Ocellated turkey.
Europe also provides room for some of those species I just listed. Oh, Europe also has puffins and Ibex! And pelicans, and swans...
Like the South and Central America split, I’d also appreciate an India pack and a separate Asia pack.
India could have a monkey species, the binturong, a Nilgai or blackbuck, maybe the Indian leopard? (I’d also adore the Indian Giant Squirrel!)
Or we could have the Sri Lankan leopard in the Asia pack, and a deer species (axis/sika?) which would look really nice with some red crowned cranes. Also has room for another monkey, and maybe takin, Himalayan tahr, or Chinese flying squirrel.
So yeah, just some of the first animals that come to mind.