The hippos do not have access to the savanna, as there is a hidden moat that separates them from the giraffe, gazelles, oryx, zebras and ostriches. This award-winning area is 30 years old and still excellent.
@DavidBrown Plans to move the zoo's hippos were shelved because of Covid, but in the 2022 Annual Plan there is mention of revisiting the idea of shifting the hippos elsewhere. The exhibit opened 42 years ago and is now considered outdated as the water still has to be drained weekly, is dirty and clogs up the drains with lack of decent filtration, has never been heated and therefore is very cold, and the indoor accommodation is not adequate for a modern AZA zoo.
As for what could replace the hippos...who knows! Maybe the African Savanna could be extended into this area, with some more antelope added? The whole thing could be netted over and leopards added. Hyenas, red river hogs, baboons, etc. The list of possibilities is intriguing.