I think we will have to make a number of changes, and that it’s an inevitability that str8 marriage is going to change as well (regardless of whether or not SSM is legalized any time soon). The fact is, more and more people are engaging in relationships that defy the traditional roles pushed onto marriageand enjoying this publicly. Women who are the primary family income, poly unions, open or semi-open relationships, etc. The explicit, asymmetric binary of marriage – where MAN takes a WIFE – is becoming archaic. I think normalization of family law, and a minimizing (if not outright removal) of federal advantages for str8 marriage are on the horizon. Maybe not for things like immigration law, but certainly for taxation and benefits purposes.
I think gays and str8s will be using new ways of conceptualizing their relationships just out of fact that the culture in which we exist is changing so much. There will be people who take a partner’s surname, or hyphenate, or leave their names unchanged. There will be lots of dual-income households, and families with extended relatives being caretakers, and all sorts of complex, non-“traditional” arrangements. It’s going to be much more up to the individuals to define what their relationship is, instead of basing it on traditions and cultural history.