If I buy a power adapter from the online Australian Apple Store, will it match Australian outlets? I want a power adapter for a MacBook Air that matches Australian outlets (without a separate adapter).  It seems reasonable that if I buy such a thing from http://www.apple.com/au, it will have the right outlet format.

Unfortunately, there's no language to that effect on the product page, and if I add it to cart there's no indication that the adapter won't be US-format.  Will adapters purchased from http://www.apple.com/au be Australian format?
Have a look at: Apple World Travel Adapter Kit

If you get the adaptor kit it works with your existing power supply. You just pop off the end you have, and slide on the new end. It's just changing out the prongs for the correct one needed.

Also works with most other Apple products.

This isn't like a normal international adaptor which sits between the socket and the existing plug - it replaces the existing plug.