The problem is, there are likely to be multiple competing proposals, and even if they aren't on the ballot at the same time, they create a lot of uncertainty. M

The problem is, there are likely to be multiple competing proposals, and even if they aren't on the ballot at the same time, they create a lot of uncertainty. Many voters will choose to avoid that uncertainty by voting to keep the monarchy. At this point, the monarchy is the default position, and I think it will stay that way until the monarch does something to piss off the majority of the Australian people.