I don't understand that logic.
As a gay man I don't have a gay driving licence. I don't eat a gay breakfast, I don't have a gay contract when I buy a house. Similarly if and when the law changes to allow gay couples to marry I won't have a gay marriage I'll just have a marriage same as a heterosexual couple. No one is creating a new thing called 'gay marriage' but rather are extending the right to marry to gay couples.