I wouldn't say Perth property won't plunge? i think all property would plunge. interest rates then fall and it all starts again. as alexlee pointed out, clear streams and mountains don't equal high property prices. there is nothing particularly aesthetic about Kalgoorlie for example.
the scenario starting with a US housing bust is kicking around all over the place at the moment. I find John Mauldin's updates particularly interesting. i can't see anything healthy about an economy propped up from US consumer spending resulting from inflating property values. real growth in GDP creates wealth, not equity withdrawals against valuations that have run ahead of long term vals.
And at the same time, just because a place has water, mountains, etc doesn't necessarily mean it will be popular. You still need utilities, services, etc and if city property prices fall, the boomers aren't going to be confident enough to just 'cash out' and move. With a critical mass of retirees shops and services will just appear, but that's assuming the retirees are confident enough to spend. Most of these people are just 'we own our own home' types who don't really know how to manage money. A economic downturn will hit their confidence hard.
Cashing out and moving is an expression of confidence in their retirement, I believe, and if the economic outlook is uncertain, they won't. They will cling to what's familiar, and that means staying put in the old house.
What's interesting is that now experts are saying flat and falling property prices in the US won't plunge the US into a recession. This despite the last 5 years of consumer spending being propped up by refinancings, and inflation kept low by shifting production to China.
For me, the more interesting question is 'in an economic downturn, which market will plunge the most'? Looking at rental yields, I say Perth. Of course, if you bought before, say, 2005 it doesn't matter much if prices fall 20%. I won't be buying in Perth anytime soon, though. I'm not selling, either, but for new purchases I'll pick markets with a bit more cushion in the form of rental yields.
Alex