The proviso being these statistics are valid, so my thoughts are that continued price rises are unsustainable.
Firstly I wonder how many properties are being bought by overseas residents, given that Rudd relaxed the rules for marketing to, & purchases by OS residents.
Secondly, I don't see incomes growing at the same rate. In fact wages in some industries have barely kept pace with inflation, & some have even gone backwards .  Sure, the flip side is some industries are flying, like mining.
Thirdly, if banks are tightening credit rules, it should now be harder to get loans, & therefore harder to push up prices.
Fourth, the First Home Vendor's Grant is no longer helping to prop up prices.
Ok, lets consider migration & new dwellings not keeping up with demand. This will put upwards pressure on rents, but there comes a point where people can't pay any more for rent, unless they choose to starve or sell a kidney. Because for many, wages just aren't keeping up.
From a residential property investor perspective, as deposit interest rates increase & share market prices / returns improve, property will need to compete with these & other investment options, especially if you are investing using borrowed funds.
Finally, I can't but help paste part of a recent interesting commentary by PIMCO's Bill Gross. While it's a general observation on the causes of the GFC, I contend that some of it can be related to where we are with property today:

' To begin with, let’s get reacquainted with the fundamental economic problem of our age – lack of global aggregate demand – and how we got to where we are today: (1) Twenty years of accelerated globalization incrementally undermined the real incomes of most developed countries’ workers/citizens, forcing governments to promote leverage and asset price appreciation in order to fill in what is known as an “aggregate demand” gap – making sure that consumers keep buying things. When the private sector assumed too much debt and asset prices bubbled (think subprimes and houses, or dotcoms/NASDAQ 5000), American-style capitalism with its leverage, deregulation, and religious belief in lower and lower taxes reached a dead end. There was a willingness to keep on consuming, there just wasn’t the wallet. Vigilantes – bond market or otherwise – took away the credit card like parents do with a mall-crazed teenager. (2) The cancellation of credit cards led to the Great Recession and private sector deleveraging, the beginning of government policy reregulation, and gradual deglobalization – a reversal of over 20 years of trade policies and free market orthodoxy.'

Food for thought.

… ok, I guess the next thing is to find out minimum residential block size allowed.
Have you considered townhouses ?

Cheers, Paul.

‘The main thing is to keep the Main Thing, the main thing’

I guess that’s always an option – if people want to invest in retirement villages or similar, you can always buy shares in those listed on the stock exchange.
Of course due dilligence, research etc needs to be done as for any investment.
There’s a couple of biggies who’s shares have made large gains in the last year or 2 – seems quite a few people are thinking along the same lines a-la aging population.

‘The main thing is to keep the Main Thing, the main thing’

To answer your specific questions:

Yes, if interest rates rise & all else stays the same (rents & other expenses), then a +geared IP can go -geared.
Same thing if rents drop.
If you’ve got 20 of these you could be in trouble!

Rents are strongly influenced by rental property supply & demand, so just because interest rates go up, doesn’t mean rents will automatically go up. However over time the bottom line is that an investment has to provide a reasonable CG/return, otherwise people will (should!) invest elsewhere – factoring in the cost of selling/buying. So for arguments sake, if there’s fewer investors, there’s fewer available rentals, which should lead to higher rents (assuming no population decline). We come back to supply & demand.

Cheers, Paul.

‘The main thing is to keep the Main Thing, the main thing’

‘Good’ television = (hopefully) lots of eyeballs = high ratings = more advertising revenue = …. you know the rest.
Nothing else matters.