I can’t say for certain, regarding the Lessers; but from what I was able to see through the construction tarp. I can confirm that the walkthrough will at least have the following:
@StoppableSan, there’s always a possibility that the Greaters are really juvenile Americans; though, I didn’t spend enough time to thoroughly identify what they truly were.
@StoppableSan, until a local ZooChatter can better clarify what’s truly in the walkthrough; I don’t guarantee that it’ll have more than one species when it opens.
It's not uncommon for zoos to mix flamingo groups, as larger flocks are more active and can stimulate breeding. Milwaukee, Denver and Indianapolis both have kept mixed flocks of American and Chilean flamingo for a while. It's a different mix than American and Greater but it's definitely not unheard of to keep multiple species together.