I can't comment on WA. However, Hervey Bay's population is now close to 60,000, with very little land avaliable within 4/k/ms of the beach. So I doubt the town will reach 180,000 as easily as you predict? Yes there is land further away from the coast, but in the long term, more development further from the coast will only increase the value of beach side land. This phenomenon has occurred all along the coast including in larger cities such as Sydney and Newcastle.
Development always begins on the coastal fringe becuase we have an obsession with that big blue thing, and then spreads further, in the case of Sydney, a lot further back. But as stated previously this only increases the value of land closer to the beach.
