I just think the Aussies play unconventional style and that may throw Brazil off their game. I could see a tie if the Aussies play inspired, and they really have no pressure on them, since nobody expects them to win. I've just had this hunch that the Aussies are going to be the 2006 version of the 2002 US team.
On the face of it I'd call your prediction nuts but the Aussies play hard in every sport and Hiddink may have some Jedi Mind Tricks up his sleeve:
http://soccernet.espn.go.com/news/story?id=371329&cc=5901
The tale about Australia fielding a weakened team to save their yellow-card players for Croatia I don't buy. I can't see Hiddink or the Aussies surrendering without a fight.
I'd love to see the Aussies topple the Brazilians and their old, fat, and out-of-shape Ronaldo, but it would be a bloody miracle if they do.