Pokemon Platinum Version was rated by the Australian Classification Board on February 6th, 2009. Platinum received a PG rating from the board due to the mild gambling references that are experienced at the Veilstone City Game Corner and due to the fact that the gaming experience may change when played online. "Computer games, whether they are locally made or come from overseas, have to be classified before they can be sold, hired or demonstrated in Australia." (ACB
A release date for Pokemon Platinum Version has not been announced yet for Australia, but it shouldn't be too far off now that it has received a rating.
Source: Australian Classification Board