The short answer is that the new same sex marriage laws will have no significant impact on Australia’s family law system.
Marriage is currently defined under The Marriage Act 1961 as “The union of a man and a woman to the exclusion of all others, voluntarily entered into for life”. A bill must be passed and amendments made to the definition of marriage in The Marriage Act before same sex couples can marry in Australia. If same sex couples marry and later separate, the Family Law Act will treat them in substantially the same way as it would have if they separated and had not been married.
The provisions in The Family Law Act 1975 that relate to parenting matters apply equally to de facto couples (including same sex de facto couples) and married couples who have a dispute about children.
The provisions in The Family Law Act that relate to financial matters such as property settlements and spousal maintenance treat de facto couples (including same sex de facto couples) in almost the same way as they treat married couples. The major difference is that a party to a de facto relationship must have been in a de facto relationship for two years or more (or made a substantial contribution to the relationship) before he or she can make a claim to property owned by the other party.
On the other hand, a party to a marriage can make a claim to property owned by the other party, in theory at least, even if they were married for a very short period of time.
In conclusion, The Family Law Act treats de facto couples in exactly the same way as married couples in relation to parenting disputes and substantially the same way in relation to financial disputes.