Based on the guesses, Tassie, Kiwi and Penguin seem quite certain. For the other slots, there's debate between the Quokka/Sulawesi Crested Macaque and Orchid Mantis/Rainbow Lorikeet.
Based on the cocktails, I would lean towards the macaque and mantis, but what theme would the pack have? All species are from a similar region, and arguably Sulawesi and all of Indonesia to its east are Oceania, but usually this isn't where the boundary is drawn. According to common definition, the macaque and mantis are part of Asia. So perhaps they could call it a Pacific pack, or something?
If we get lorikeets and quokka, Oceania is a logical guess. I assume that we will either get both of these, or both of the other picks for thematic reasons, because why would they include exactly one species restricted to Indonesia and one to Australia?
Other options are still possible of course, but make the mystery only bigger to me. If the exhibit species is a hummingbird, what will that mean for the theme? All I can think of is Tropical, but we just had that earlier this year. And 'Exotic' seems too vague and not a term that you'd wanna use these days anyway.
The most logical option considering the most recent packs would be Islands, but this brings us new problems. While it would work with the macaque and the mantis, it would be weird to have an Islands pack without Caribbean species. But then we just had the Arid DLC...