If the Baboons moved to Werribee, there enclosure could be freed up for the Spider Monkeys. Possibly adding in another South American Species, could possibly hold the offspring of the Brazilian Tapir if they are imported.
I think currently it is unlikely for a Gorilla Expansion, it would be costly and unless the zoo wants to take the 3 males from Weribee it would make little sense
However the redevelopment of Tree Top Apes and Monkey seems likely in the coming years
Species
Cotton Top Tamarin- Stay in this area
Emperor Tamarin - Stay in this area
Spider Monkey- Moved into the current renovated elephant complex or H Baboon enclosure, or possibly stay in this area
Colobus - Moved into mandrill enclosure, possibly introduced with Pygmy Hippo
White cheeked Gibbon - This species best suits the Asian Precinct, either a new enclosure or using the island in the lake and expanding it.
Tree top apes and monkey then would be converted into a netted enclosure with Lizards, Birds, Tamarins and other South American species if they are imported such as the sloth. It would be a walkthrough enclosure however there could be barriers between the guest meaning that they couldn’t go into the actual enclosure.
The Elephant precinct is going to be costly to redevelop, whilst it would be great to see this completely redeveloped, for the minute the think a quicker fix is likely which should be Tapir, possibly a species of antelope and orangutan expansions
however the other possibly is that Melbourne could choose to import Greater One horned rhinos, display them for a few years once funds improve, then move them to Weribee and redo the precinct, the tapir if imported could either live in one of the elephant enclosure, or possibly in the current nyala one. The nyala would be moved to the Bongo enclosure and introduced with the giraffe