I have been looking at the Joel Anderson website, and I note that he has a fantastic array of current 'Interesting Stuff' world coinage.
I seems to me that if Australia introduces a 5 or 10 dollar coin, that they would be most probably be bi metallic; he has a very extensive array of such material on offer.
I have a very extensive 'just for fun' collection of square coins, and I have bought a few of these off him. It is certainly a different type of website for an American dealer.
I have been studying and collecting ancients for decades, but looking at his website is light relief for me.