Gakked from elizabear the article is a thoughtful and neutral treatment of the subject.
My personal observations are that this is the logical continuation of the social change that began with divorce at will and continues through same sex marriage. If we accept the premise of marriage as entirely self-defined to mean "some formalized (or formalizable) relationship defined between consenting adults for the purpose of organizing economic and social activity," then the logical end point is along the lines of The Moon Is A Harsh Mistress where people develop whatever set of relationships resolves the pragmatic details of property and care of children until they reach majority.
My other observation is that I've never observed any great magic about poly over non-poly or non-poly over poly in terms of eliminating the game playing that goes on in relationships. From my limited observation (which for me personally is so boringly standard that it counts as exceedingly rare these days, so I'm relying on anecdotal observations) people remain pretty much people with all the foibles, virtues, and neurosis to which humans are heir. People seem to have an endless capacity for breaking rules, as well as keeping them, regardless of the number of relationship partners.
Taking these two together, 21st Century family law should grow increasingly interesting, especially as hidden prejudices (and no hidden prejudices) play out in the judiciary.