The Black and white colobus troop are an ageing troop, so I’d take a new purpose built exhibit for them as a sign of a long term commitment from Zoos Victoria. They’re breeding well at Adelaide, so it wouldn’t be difficult to source more long term. In the meantime, they could easily occupy the old Mandrill exhibit as you say. I’m not really sure why that hasn’t happened already to be honest.
I too am not completely sure why the former Mandrill exhibit has not been occupied by the Colobus yet if that was the plan. Obviously it isn't suitable for them as of yet - ropes and platforms would need to be added; but those are relatively easy modifications. Zillie's transfer back to the GFA last year seemed to indicate the zoo was finally moving on with redeveloping/modifying that enclosure for a new species, but there's seemingly been no progress since.
It does make me wonder whether Zoos Vic actually do intend to display the Colobus there (as we have theorised). Perhaps they're waiting for confirmation on this new Ropes course, of which could lead to redeveloping the exhibit too ie. there's no point in redeveloping it now and then again, in five or so years time.
We will hopefully have clarification in the coming months whether Brazilian tapir will join that precinct; though I can see Lupo remaining where he is, with the peccary exhibit becoming an extension to accomodate a female long term (5+ years depending on how long the peccaries live).
The elephants were definitely the zoo’s biggest drawcard, closely followed by the gorillas. Unless the zoo are going to loan a pair of Giant pandas, I struggle to think of a species that could meet or exceed the popularity of the elephants; but a few alternatives could be:
South Asia: Indian rhinoceros, Asian waterbuck and Indian antelope
South Asia: Sloth bear (probably a little too ambitious, but would be incredible).
South East Asia: Sumatran tiger, Sumatran orangutan and Siamang (expanded facilities for these species, all of which are already housed within this precinct), Komodo dragon
Central America/South America: Brazilian tapir, Black-handed spider monkey, Bolivian squirrel monkey, Xenarthra
Sloth Bear would be huge, but as has been stated previously, they're a difficult species to work with when you consider the populations overseas aren't doing the best.
Leaning into the South East Asia theme is probably the most likely. An Orangutan and Gibbon expansion complimented by Komodo Dragon is the obvious suggestion. However that still leaves space for something else. The obvious suggestions being;
A) A Tiger expansion - combined with a new overhead pathway connecting the two habitats would be spectacular. That's likely if Melbourne wish to continue breeding the species, and would allow them to upgrade the current habitat too at the same time. Very possible.
B) A South American extension. Enclosures for Brazilian Tapir. Very possible too. An extension of this could also be supporting enclosures with the likes of Spider Monkey and/or any new Xenarthra species. Also a possibility, especially if they create a walkthrough aviary style enclosure in perhaps the largest elephant paddock. Not as likely, but still a good chance. Overall it would create a generic Rainforest trail (which isn't bad).
C) Perhaps in line with a South East Asian precinct, a large walk through aviary or a Tropical Dome (similar to Auckland's). I'd appreciate seeing more diversity around Melbourne, and the two Rainforest trails in particular really lack diversity aside from mammals. Zoos Victoria have recently gone in the direction of displaying some invertebrate species in the Forests of Wonder trail, so it gives me hope they'll really look at a more diversified precinct. So whilst unlikely due to the funds that would be required; certainly a 'watch this space'.
