Suddend drop of demand will do the trick.
What will do the trick is affordability, particularly for low income areas. That's where it will start if it does, and if prices go down in low income areas then expect the problem to spread later to higher class areas. It depends a lot on many factors though.
All the same I'm happy to wait for now. I definitely feel that houses are overvalued atm and there are signs that people on current real wages can not take anymore debt strain. In other words no one to finance my capital gain.
I see money supply increasing; I don't want to jump in and finance the profits of generations before me.
Besides why do that when I can enjoy myself for awhile? When and if the market picks up again and is on a 'trend' I can jump in. Sure maybe a little bit higher but then I have more certainity in regards to the investment.
EDIT: If I don't see incomes rising (due to economic conditions deteriorating) or debt levels being able to be increased even in times aplenty then where is my capital appreciation going to come from?