The biggest argument against a pack "barnyard/petting zoo" pack is the fact that most of the animals aren't particularly highly-requested. But, despite that, I feel like people have been steadily requesting many of the petting zoo features since the game's inception up through 2023. And you kinda need the animals to justify that. The question is: Would it offset the people who would be really bummed and not want to purchase the pack? TBH, it probably would.
And if they went with "domestics" instead of barnyard for the scenery? You could get that dromedary in-game. Which might appease folks a bit. Especially if they went for an exotic pig species, African pygmy goat, and a rabbit for the remaining animals. It would also open the door for budgies! It would make the pack feel a little lopsided in terms of animal picks but...
Regardless, the big draw for me, I think, would be the scenery. A clapboard wall set. A new fence type. Stone wall scenery items (including rubble to show age/wear). New feeder types and troughs. More backstage-type items. Smaller mesh pieces. Focusing on "farms" could be a nice way to add more of that "general zoo" scenery people have been asking for.
And when you think about the other options (e.g., "islands" or "highlands" or "forest") I'm struggling to think of scenery that would make sense - and would align with the animals. "Tropical/jungle" is the one theme I can think of where scenery would be awesome.
If it's an animal pack and we get domestics? I would probably be bummed. But I dunno. It would be a bigger disappointment to me if we got a "forest" or "tropical" scenery pack knowing how many animals of that type people are really wanting in-game... To me, it just means there's bigger things coming in terms of animals. If that makes sense.