The current complex Taronga will have them in will give them the opportunity to separate the Water Buffalos from Hari when desired.
Initially, it's been advised the two species will be kept separately before introductions commence with the goal being to have them as a mixed species display down the line.
In the long term, Taronga do have the facilities to breed as has been mentioned. In the event that occurs, the Water Bufallo could easily be sent back to Dubbo.
If additional zoos don't end up coming on board regionally; the best option would indeed be to utilise Taronga's facilities for an additional breeding pair imo.