Happy birthday, Jesus!
That's probably about what we'd do here in the states if we had a referendum today, sadly.
We already have it here in the states.
What state is left that continues to define marriage as only between one man and one woman?
I dont know of any. So the battle is already lost here, literally, until Society by and large retuns to a foundation rooted in God. Or until Jesus returns in Glory. And I dont see either happening in my lifetime.
At least Oz did it by referendum, instead of by fiat like some states (judges) did, just changing the definition via law suits instead of legislation.