Same-sex marriage always had forward momentum, due to Americans love of fairness and minding out own business. It was inevitible, I would say.
Defining "woman" as anyone who says that he or she is a woman* has no such momentum, and will soon be on the ash heap of history.
We want to exclude men from women's sports and women's spaces due to the same fairness and minding our own business (yes, our mothers', wives', daughters', and female friend's safety and opportunities are our business to protect).
*I assume that is your definition, even if you are unwilling to admit it. Your lack of comment will be the proof.