Hey, I'm Australian too and I think the answer is never or at least not for a long time. If you desperately want a boxed copy then you can order it from Gameplanet New Zealand for $100 NZ (like $80 Aus).
But by far the best way to order is through Gamersgate. Check them out. I can highly recommend this service providing you have a way to download the game (which is a 2 gig download). It will cost you about $60 at the current exchange rate, which is much cheaper than the alternative. You're a bit late, I got this game three weeks ago and I only paid $48 due to the better exchange rate to the US dollar.
But go with Gamersgate. I have bought three games from them and I've never had a problem.