Our preference continues to be to say and write "same-sex marriage" or "marriages of same-sex couples" rather than "gay marriage." In some listeners' and readers' minds, a "gay marriage" is between two men. In addition, the AP Style Book's entry on the word "gay" says that "lesbian is the more common term for women."
"Same-sex" addresses those issues.
Also, "gay marriage" is a mislabeling if one, or both, of the partners is bisexual. They are not gay or lesbian. But some bisexuals are in, or wish to be in, what listeners and readers can understand are "same-sex marriages."