The Zoo spent $50 million on Asia Trail and it's the most popular section of the Zoo. They'd never level it for Africa after only 20 years. My bet it remains empty for quite some time.
Yeah people can speculate all they want but until zoo leadership believes with 100% certainty that pandas ain't returning there's in my opinion only two scenarios that are gonna happen, the exhibits just sit empty or another species is brought in to temporally fill them that requires either no changes or a very minor amount of changes to the current exhibit.