I think the chance of us getting another Australia/Oceania revisit is virtually null (but then again I thought the exact same thing until that fateful night Oceania was teased lol), but if I had to design one based on Frontier's possible new style of easy to make animals I would do it a little something like this:
Eastern Quoll - Made with some minor changes to the Tasmanian devil rig, the eastern quoll provides the game with a second dasyurid and the only quoll species currently kept outside Australia. They are especially attractive thanks to coming in two common colour morphs, fawn and black (pictured).
Yellow-footed Rock-wallaby - As well as giving us a wallaby species from more arid climates, the rock-wallaby would also be unique among Australian animals in the game in requiring a caprine-like rocky habitat. Hopefully it would be given a new animation to use the goat climbing mountain.
Eastern Grey Kangaroo - Temperate Australia is part of the continent that is most well-represented in-game, but it'll always feel like its missing something without its own kangaroo. Also provides a more biome-appropriate species to mix with the red-necked wallaby.
Black Swan - Should require no explanation, a second waterfowl species (even if another swan) that is extremely widespread in captivity around the globe.
Black-necked Stork - The game's first stork, the black-necked stork is an impressive and iconic bird of Australia's tropical northern wetlands, where it is commonly referred to as the jabiru (not to be confused with the South American stork of the same name). As a bonus the species also occurs in south and south-east Asia, adding more avian representation to two continents.
Freshwater Crocodile - Gives us a smaller (and better looking) alternative to the giant saltwater crocodile, and would also hopefully come with a new galloping animation when running on land. If we can have 5 North American canids a second Australian crocodile can't hurt.
Perentie - The king of Australian lizards, finally gives the continent a species of monitor lizard and is arguably the most essential missing animal when it comes to fleshing out Australia's desert heart. Plus they just look stunning.
Probably my favourite thing about this pack is how it helps to flesh out most major regions of Australia - the quoll and grey kangaroo represent the temperate regions, the perentie and rock-wallaby the deserts and the stork and crocodile the tropics (especially the great northern savannas, a vast region we have very few species for in-game), whilst the black swan occurs pretty widely.
