Gonna run some of my own imaginary numbers, on some of the more likely themes and more likely animals (all just my opinion of course). The numbers do see a significant drop after the top spot, but not every animal works as well for so many packs. mostly sticking with more popular animals from the metalists, but throwing a few that show up on some of the more strongly discussed pack ideas.
The Wolverine - 90% chance of inclusion- works for Alpines/Highlands, Tundra, Eurasia and even Woodlands at a stretch. It's also a very highly requested animal, and is one of the more iconic mammals left to include - though it's not instantly recognizable. Unless it's Latin America themed or something completely unexpected, they've got the best chance of any animal making it in.
The Walrus - 70% chance of inclusion - works for Tundra and Eurasia themes, and it's very highly requested, and is probably the second most universally recognizable zoo appropriate mammal not in the game, behind the general rabbit family. We also haven't gotten a penniped in over two years.
The Muskox - 60% chance of inclusion. works for Tundra and Eurasia and is highly requested. Not as universally recognizable, but not obscure by any means.
The Spectacled Bear - 60% chance of inclusion - taking up the other spots the last two didn't take, it would work for Alpines/Highlands and Latin America. It's not near the top of the meta lists but is one of two animals that seems to be on nearly all Alpines/Highlands lists along with the Markhor - both of which are in the metalist top 20. We haven't gotten a bear in quite some time either. Not universally recognizable in that the average person would only see them as a "bear", not a specific species of bear.
The American Black Bear - 50% chance of inclusion - noting that of course we'd only get either the Spectacled or Black Bear, so one would defintiely negate the other. Would work for Woodlands, Tundra and even Highlands (though it plays a very distant second to the Spectacled Bear for highlands) - they're very much a nearly every biome type of animal. Inarguably missing iconic North American species. Ranks quite a bit lower on the various lists in comparison to the Spectacled Bear but still within the top 40.
Black (or Red) Howler Monkey - 30% chance of inclusion. Really only has a shot if it's a Latin America type of release, but a pretty high one if it is that type of release Most of us have been begging for additional New World primates and this is the most likely inclusion for that theme. Probable preference to Black but I wouldn't be surprised if they went with the Red Howler instead.
Markhor - 30% chance of inclusion - Really only works for the Alpine/Highlands pack, but is one of the near-universally agreed animal to make it in that theme. Talk of more Asian ungulates has increased so it may have that in its favor too, albeit only slightly. Is top 20 in the metalist at this point so while it's not critically requested, it's still got a lot of support.
Ocelot - 30% chance of inclusion - Only really works for a Latin American theme, but we know how Frontier loves the cats. Top 20 in the metalist as well, so while not critically requested, it's still very popular.
Gelada - 25% chance of inclusion - works for a Highlands pack but it doesn't have quite the same pull as the Markhor or Spectacled Bear. On the other hand, while it isn't specifcally a baboon, it is close enough that it may fulfill that spot in the roster. For a while anyways.
Coatimundi (any species) - 25% chance of inclusion - Also only really works for the Latin America type of release, but is critically requested. The reason I put it slightly below the Howler Monkeu and Ocelot is the additional work the rig would require comparatively, but in truth I suspect we'll get all three if the release is Latin America themed.
Takin - 20% chance of inclusion - works for Highlands, and is highly requested. It really doesn't have much else going for it though, which is why it ranks as low as it does.
Hamadryas Baboon - 15% chance of inclusion - It doesn't really fit any of the themes directly, but it might could be worked in the Highlands pack as a stretch. As opposed to the Gelada, it is the most requested Baboon species, so it does have that going for it.
Wild Boar - 10% chance of inclusion - Prior to the Collared Peccary Anniversary gift, I would have put them closer to 40% chance of making it in, but not now. I do think we'll get them at some point, but not right after we got a fairly similar animal for free. They're nearly at the top 20 of the metalist, but not quite.
Tamarins - 10% chance of inclusion - probably more likely as WTE animals than habitat animals, but this would be a high chance of being included in a "non-Central American" Latin American focus, with the Golden Lion Tamarin being the most likely. It's also right at the top 10 mark on the Metalist.
Secretary Bird - 5% chance inclusion. Nothing's impossible, almost anyways. It fits none of the majorly discussed themes, but the fact it's sitting at the top of the metalist means we shouldn't count it out completely.
Tree Kangaroo species - 3% chance of inclusion - like the Secretary Bird it doesn't fit any fothe majorly discussed themes, but it is a top 5 metalist animal. So I wouldn't count it out completely, though it doesn't have the advantage of being at #1 like the Secretary Bird.
West Indian Manatee - 0% chance of inclusion - The "almost' in the nothing's impossible, almost" referenced above. It's a fully marine animal and currently the game doesn't support fully marine animals. Oddly enough, it fits in with the Latin America theme, but it's a matter of game mechanics not just animal inclusion.