It would be viable if the British did not change over, and if there wasn't the changes in trading relations with Britain joining the EEC; even then, this leaves out a host of points related to earlier trading developments, politics, and the nature of the Australian economy.
Now, if for some reason it does continue (setting aside the reasons why) then we are going to encounter difficult maths sums for schoolchildren as they learn the system, but no dislocation at the other end from those used to the old system; not that this was an extremely great factor historically. A difficult system is not a bad one in and of itself, just as an easy system isn't a good one in and of itself.
It would not have the same effect on standardization as weights, measures and distances.
It would also lead to some difficulty for tourists from decimal countries.
Apart from those points, it wouldn't have any great effect on the Australian economy, and certainly no more than a historical footnote.