Well first of all it's not official that Australia are now on the decline, or that our period of dominance just finished, our period of dominance (as in being unstoppable, unbeatable) has clearly been over for several months now.
The only thing we are discovering now is how deep the decline might be, although it seems pretty clear that our current ODI team is nowhere near our best, we're still missing Lee, Tait, Siddle, Marsh, Symonds, Watson and Ponting from the team that lost yesterday. You can also throw in McGain as I reckon he will find himself in the ODI team in South Africa, he only just got back from injury on the domestic scene.
I still think that our test team at its best can be number 1 again, and our ODI team I'm not sure, but our current lineup is severely weakened.