I'm an Australian and I see absolutely no sense in changing at the moment. I think our political system works fairly well, I'd rather keep it as far away from an American system as possible (Seriously, how do you guys expect anything to get done when Obama only has majority control over one house :s). The Queen has no real power here anyway.
This has absolutely no chance of happening whilst Elizabeth is still Queen, the vast majority of the people like her, once Charles is King (if he doesn't die before her of course) then maybe. People seem to want to change out flag when becoming a republic too, but every alternate design I've seen has been awful. Green and Gold are not an appealing mix on a flag at all (Sorry Brazil) :s The National Anthem though could use a change (NOT Waltzing Matilda, I am Australian or True Blue, they're all awful without giving them the spectacle of being an official anthem)
