I hope we are able to trade between our own zoos. In Zoo Tycoon 2 you could select zoo sites from plots around the globe; I hope we see something similar in Planet Zoo. Then say, for example you establish a breeding program for the duck-billed platypus in an Australian zoo (species currently not held outside of Australia) and produce a surplus of animals that you could then offer to your other parks. i.e. animals are only available for trade if they actually exist somewhere in your Planet Zoo world. It would be a great feature to keep people playing, and encourage them to establish multiple zoos and use different maps. I would love to see certain species only available in certain locations (e.g. pandas in china, platypus in Australia, pronghorns in America).
I personally hate multiplayer games, so I hope an online market where we have to rely on other players to offer trades is not the only option.