I would like to see us hit at least 200 animals so 20 would be nice, but there's no guarantee of anything extra so they could just stick to the standard 7+1 animals. which I'd be a little sad about.
I think if it were to try to hit 200 animals we may get a lot of clone animals (Masai Giraffe, American Flamingo, Grevy's Zebra, Rhea) due to the resources needed to make new rigs. I'd be honestly ok with this as long as we still got 1-3 new rigs. I don't think they'd focus on one particular area or biome. I think it'd be some kind of global safari pack to be able to include animals from all around the world. It'd also make a lot of sense if they added 1 more animal for each DLC/Upgrade so 17 + 2 Exhibits. I'd hope they'd at least include 1 more bird, 1 more New World Monkey, and something from the Patagonian region.
I think we'll probably still get 1 more anniversary animal too, hopefully something for the Walkthrough Exhibit as there are currently no base game animals for it.
I'm really hoping we get at least two packs though. I'd like to see the spring pack be a petting zoo/children's zoo scenery pack, which will make a lot of people happy and also upset a lot of people but I feel it's a needed addition. Then the next pack be would the larger end of support pack. This would make the game feel pretty complete for me at least.
Edited to fix typo.