I could actually see national zoo and aquarium being a place that be interested in river hippo, as well as Australia Zoo.
It will be interesting to see what out actual capacity for river hippos is, and what the zoos are willing to hold. If breeding is done sporadically, whether the open range zoos with cohesive female groupings currently. Breed then reintroduce females and offspring back together again, to try and create large pods.
Australia Zoo is a strong likelihood in my opinion. They have the space and the money should they choose to invest in building an exhibit for this species.
I’m assuming zoos won’t be castrating surplus first generation bull calves, but it was used to effectively manage a mother-son pair at Auckland Zoo long term and so could be a consideration were there to be a wave of male births.