This post by Terry McFadgen on Australian housing prices is a good summary of the question of if/when prices will tank. One thing overseas readers should keep in mind is that Australian borrowers can't walk away from their debt - the bank can foreclose on you and then go after you or bankrupt you for any remaining debt not paid by the sale of the house.
As you would expect this dampens the negative price spiral that can occur in countries where walk away is an option. However, consequence of this is that in the face of financial difficulties people will tend to restrict other spending and divert money to paying off the mortgage to avoid the stigma of bankruptcy (although this doesn't seem to have bothered "former tennis ace"
Mark Philippoussi) This contraction in discretionary spending acts like the “Paradox of Thrift” Terry mentions in his article.
I think Terry makes a good case that "house prices could simply slide down gently over a long period, with inflation doing most of the work of price adjustment" but he does identify four risks/shocks which could bust prices.
He notes that the RBA is between a rock and a very hard place in trying to de-bubble housing but having to increase interest rates too much to control inflation, or having to cut interests rates too much if housing tanks which will weaken the Aussie dollar and stocks as foreign investors pull out.
My view is that push come to shove RBA will cut rates and damn the exchange rate as an imploding housing market is not good for banks and the political pressure will be too intense. This will be an extend and pretend that will work for a few years as there is plenty of room to move with interest rates at the 6% level. A weak exchange rate is good for AUD precious metals prices, by the way, a sort of hedge against house price drop in a way.
I would also not discount politicians doing something stupid to "help" housing. With debt to GDP of 20% a populist call to "do something" could be made when other countries are at 100% ratios ("we have the capacity"). It will all be wasted of course but could drag the game on a bit longer.
However, as the US shows us, once you get to zero interest rates you've got nowhere to go and QE doesn't help housing. Once we reach that point then we will really see a housing price crash as the boomer demographics, China slowdown and "income levels [don't] hold up relative to interest rates" factors all kick in together.
To sum up my view on house prices, "It Won't Happen Overnight … But It Will Happen" (
explanatory link for non-Aussies)