I do realize he is dead, and I do understand how the Supreme Court works. I attended law school at The University of Colorado and practiced law for three years in oil and gas before going into the business side of energy. So I am decently well versed in constitutional law, amendments, the role of the justices, etc.
Let's say Hillary appoints a judge, and Hillary does in fact like the Australian model. I have also heard that Obama likes the Australian model, and yet here we are, eight years later, and my gun rights are still intact. But let's take on your issue...
To have a case before the Supreme Court, we would first have to have a challenge to an existing law. No existing law is going to be challenged on guns because those have already been litigated. So there would need to be a new law enacted. To have a new law enacted, first we go through the House, then we go through the Senate then the president signs that into law.
The only thing congress can agree on lately is that they all deserve lifetime pensions no matter what, and that they get a raise every year. Outside of that, they don't agree on anything. So even if Hillary were to push, lets say a total ban (she wont, political suicide and the money in the gun lobby is insane) you are going to assume that passes the house and senate, before any Supreme Court justice gets a crack at the analysis. All GOP'ers would likely vote no on the bill, so it would rest on the democrats to pass it. With both houses currently under GOP control, that would be tough. Add on to that states like Colorado, that lean blue with their electorate, but that no representative from here would ever vote for a ban. Coloradoans (me included) love their guns. It is a political non-starter here.
For one, I do not see Hillary pursuing a ban as likely. She has never advocated for a total ban. Both her and Obama have said the like the Australian model (I'll take your word for it) but nothing has changed here in the last eight years. Expressing admiration for something that works abroad does not necessarily mean they can pass it here. And personally, I think she knows that. She might WANT a total ban (I do not think that is the case, but lets say it is), but she is no idiot (you can disagree with her ideas and methods, and you can say she does dumb things, but she is not actually dumb) and she is a career politician, this would be a losing battle to pick. So I think it would be highly unlikely for her to pursue a total ban, or the Australian model. Add on to that the fact that our country has far bigger issues than guns, and I do not see that issue getting a lot of traction.
What I DO hear Hillary talking about is background checks and maybe a ban on assault weapons - these seem to be her main gun platform issues. I am ok with background checks, and while assault weapons are a blast, I am not going to sit here and tell you it is my constitutional right to own one.
I would not support the Australian model, or an interpretation where only the army and national guard are allowed to posses guns. But I do not see that happening here. Americans like their guns too much, and I do not think the support nationwide is there for a total ban - it would never make it through congress, even if it ends up being controlled by the democrats at some point in the future. There are enough gun loving democrats out there to keep things in check. It would be total political suicide and a complete non-starter.
So long story short - political suicide, no nationwide support, guns are in our fabric and they are not going anywhere.