In the SMH on 28 December (Sidestepping the seven-year itch) David Humphries wrote “This is not an argument for the states' supremacy, or their abolition, a constitutional nonsense given the effective impossibility of removing the states by referendum.”
I've heard lots of similar commentary over recent times, and would first claim that just because something is hard doesn't mean it is impossible - effectively or otherwise. It is possible that a requisite referendum could be past in every State.
However, there really is a relatively easy way to abolish the States, amend s51 of the Constitution so that the Federal Parliament isn’t restricted about the fields they can legislate in and slowly the States can be eroded into irrelevance. The operation of the provisions about Federal law having precedence over State laws mean the Federal Parliament can legislate the States out of "effective" existence.