You do realize that all the republican movement in Australia (which is alive and vibrant) wants to do is find a republican model of government that enough people can agree on, get it put to the people as a proposed constitutional amendment, and pass said amendment? They couldn't give a flying fuck who the "rightful heir" is (hint: the body representative of the people has spoken on that, multiple times now) and certainly don't need England's "permission" to ditch the monarchy. (For that matter, the UK could ditch the monarchy if they wanted.)