So here is the most common species in european (+a few other regions) zoos, with domesticated and aviary birds removed. Animals already in the game are crossed
So how likely are the rest to get in, in your opinion?
Going through all the ones that haven't been added yet:
Red-eared slider: Niche is covered by the diamondback terrapin and if we ever return to exhibit boxes I think there are other niches that we'd would want to see covered first.
South American coati: One of the top meta-wishlist animals at this point so I kind of expect it, but its obvious chance was the Tropical Pack. The white-nosed coati (uncommon in Europe but very common in North American zoos) is a possible curveball
Greater rhea: Obvious choice for South American representation, but I hope the next bird isn't another ratite. Want to see it at some point though.
Black swan: In my dreams. Would be a fantastic addition but I'm sadly skeptical of Frontier ever adding more than one waterfowl, and I'm inclined to think it would be a duck instead.
Wild boar: Solid chance of being added in the next temperate/forest-related pack, has been gaining steam in the community, but Frontier might wait a bit before dropping another pig.
African spurred (sulcata) tortoise: Hard call that this is the next (and possibly final) habitat reptile. If we can get a third monitor we can get a third tortoise.
Ball python: Definitely see several snakes as more likely than this one. Not really distinct enough. Again, there's a degree of uncertainty around these exhibit animals.
Bearded dragon: Possible wildcard for a desert/Oceania pack? Exhibit discussion applies.
Patagonian mara: My most-wanted mammal and one that might have caught Frontier's eye at Shepreth. Would probably lose out to an African crested porcupine for the rodent slot in a desert pack, but then again we got the beaver and prairie dog in one pack.
Common marmoset: Pushing the size limits for habitat animals, would be possible but kind of disappointing as a walkthrough exhibit. Probably also not the top priority for another New World monkey.
Ferret: Like a domestic ferret? Or a polecat? The latter is a semi-plausible wildcard pick, don't really expect the former.
Indian crested porcupine: Community seems to prefer the African crested.
Greek tortoise: It's going to be the sulcata.
Leopard gecko: See bearded dragon but swap Oceania for India.
Roe deer: I think the demand for European deer is fully satisfied.
European pond turtle: See red-eared slider.
Veiled chamelon: The single most likely exhibit animal, though it could easily be a Jackson's or panther instead.
Demoiselle crane: Another crane will almost certainly be the grey crowned. I'd love this one too but you know Frontier and birds.
Helmeted guineafowl: Reasonable for a variety of packs (safari, children's, domestic, etc.) but I don't know if they'd make Frontier's cut for any of them. I really want it though.
Chinese (Reeve's) muntjac: Actually very plausible for a future temperate or Asian pack. Prominent in Britain due to its invasive status.
Eurasian brown bear: No.
My ideal "common in zoos" animal pack given these parameters, and also taking into account what an American list would probably look like, would be something like:
South American coati
Patagonian mara
Reeve's muntjac
Grey crowned crane (only deviation from the OP list)
Black swan
Helmeted guineafowl
Sulcata tortoise
Veiled chameleon (E)