F111 and all,
The cost of an ILS is approx 6million (includes the cost of upgrading approach, runway lighting, flight inspection etc). The ongoing maintenance is approx 1million/year. This will not happen at Cooly (actually now called Gold Coast) for the reasons others have outlined regarding cost and probability of wx below minimums.
As to the so called "curved GPS approaches" that F111 refers to these were part of a project known as GRAS (which is a regional based augmentation system for GPS) which has very little support within the Australian aviation community. It has been an ongoing project for years sucking millions of dollars in funding but will not fly in Australia (maybe some third world country).
As for decommissioning ILSs by 2012; based on the recent ASTRA and GIT (gps implementation team) meetings this is also a non event. ILSs are an integral part of the GPS back-up network along with a number of strategic VORs and NDBs.