Exactly, because that would be the main draw of the sequel: aquariums, birds, and niche animals that either didn't make the cut for PZ1 or just couldn't be added because of technical constraints. A sequel should build upon the foundations of the first game.
I would like it if PZ2 had vastly improved management, less irritating menus, a way to track your released animals, actual individual animal personalities, more unique behaviors for respective species, interspecies interactions, less irritating hitboxes, better AI, much better climbing, animals and fur that looks accurate from the start (like the poor orangutan that looks like a puffball), rescue/rehab/breeding/education programs. Things that feel impactful, since these games are supposed to be about conservation and education. And of course the addition of free built aquariums, various exhibit sizes, and flying aviary birds.
Oh, and a completely new pathing system. I've gotten used to the current system, but it could be a lot better to say the very least.