Luna Park Melbourne's size makes it almost impossible to be a location. They are restricted to all attractions being inside the scenic railway track
Funfields is a strange one, imho currently the best park in Victoria, but it's location is awful, just nowhere near arterial roads. Also the only space they have left is on a steep hill. Although it's a top little park, it's just not designed for much future development.
Gumbuya as we now know it seems is all but certain to get it. The park has deep pockets with investors including the owner of Jayco and Carsales.com, its desperate for big ticket non water attractions and the location is very attractive with it being located on the M1. When the park first reopened in late 2017 they advertised that they would be open 364 days a year..... that changed when they realised the lack of attractions they have outside of summer. Ever since the owners rebranded the park from Gumbuya Park to Gumbuya World they have spruiked it up to be the best theme park outside of Queensland. Getting Buzzsaw and another 1 or 2 big ticket attractions would not just do that but would also take a lot of probable customers from Funfields and Adventure Park.
Past history with Gumbuya World is they won't announce it until they have all details for phase 3 of their redevelopment of Gumbuya Park done. Who knows when that will be but would think it would be before Xmas