Truly, an obliteration of any meaning to the word "marriage."
Really, I think we should start over. What is marriage, in the eyes of the state? Why should it grant special privileges to encourage it? Does society reap benefits from having a man and a woman committed to each other? Does it benefit from having eight people of varying sexes and self-declared genders semi-committed to one another in varying degrees? Are we prepared to draw a line somewhere and - gasp! - judge some unions better than others?
If we don't have widely-accepted answers to that, maybe we should stop recognizing marriages legally, substitute designations like "this person can make decisions for me if I'm ill," and leave marriage to be a religious designation only.