Central America would be fantastic for animal representation (especially since, in an effort to make a zoo modeled after various small to medium-sized Northeastern institutions, you need a lot of Latin American animals) but it hits the Southeast Asia problem of not having an obvious star/headliner. Then again, the lynx was the headliner for the very successful European Pack, so maybe a white-nosed coati could work (ocelot might as well but I don't know that they'd do two mid-sized cats in a row?).
Two other possibilities--a Madagascar pack, which would kind of fit the seasonal pattern and bring some interesting animals (ideal mix--fossa, sifaka, two of insert African wading bird, nile crocodile or radiated tortoise), or an East Asia pack that builds on the existing scenery (which is somewhat plausible based on datamining) and includes the Amur leopard, Przewalski's horse, Sichuan takin, and red-crowned crane...but a scenery pack that doesn't have a new scenery theme is itself fairly odd. And it's still far from a guarantee that the April 12th deadline for a scenery pack is even happening (a later release is very possible). Which is to say, we're entering uncharted waters...