If my memory serves me well,
SACL has first dibs on any new airport in the Sydney basin. So apart from all the political posturing, point scoring and general blowing of smoke up everyones butts, it'll happen when SACL is good and ready.
And the dollars involved will preclude anyone else from staring up in opposition.
They will eventually get their way, excluding small regionals, and helping Qantas get rid of most of those pesky maintenance hangars so that more room can be had for widebody aprons, car parks and shopping centres and generally continuing to be on a nice little earner.
See you back here in 10 years for the next installment. Oh hang on. I'll be retired and won't care. There you go.