澳幣幾時先會跌?

In my personally opinion (though I'm not an economist, just an Aussie observing the changes!), the Australian dollar won't be below 7 HK dollars for a while, depening on the US dollars and other factors, such as oil and food prices, the war in the Middle East and natural disasters in recent days in Asia.
The US economy went into recession earlier than anyone else, and this helped theAustralian dollar to be stronger. As of today (17th May), the Aust. dollar is tradin at almost 96 US cents. This, I think, it due to the further recession in the US economy.
So unless the US economy improves, the Australian dollar will continue to be at this high level with the US dollars, and thus, with other curruncies around the world, including HK dollar. Then again, HK dollar is doing not so well with RMB either, so it's affected both ways.
These are only my observations and not expert opinions at all. Hope that helps.