Abortion is the most vivid case of a major change that still not accepted by a large chunk of the population. The problem is that it's always been decided by judges. Segregation was originally banned by court orders, but when Congress outlawed it with the Civil Right Act the issue was settled. Now praising a segregationist can cost a Senator his job. Abortion keeps getting fought over in supreme court appointments and with laws designed solely to create court cases. If we'd tackled this by passing laws we'd probably have had a solid majority for a compromise law (maybe like France's) and the issue would be settled instead of constantly popping up.
I suspect this isn't a bad thing from the viewpoint of individual politicians. Right now they can pick one side to give lip service to and collect donations and volunteer labor from the supporters, while avoiding giving any offense to the moderate majority by pointing to the courts and disclaiming all responsibility for what actually happens. But those career benefits for politicians are promoting constant battles which are toxic to our polity.
So as a supporter of gay marriage I'm hoping more state legislatures legalize it, and the example of those states convinces others to follow in their path. That's progress that will settle the issue.
I don't expect the opponents of gay marriage to give up any time soon. They're fighting to protect their culture, one where people have defined roles as part of a community and are expected to carry out their obligations. That breaks down if people are free to create their own roles in life and abandon duties they hadn't agreed to. That breakdown is well under way. The "inherited obligation" culture used to dominate this country, now it's a minority, and many of the supporters of the culture find themselves choosing individual career goals over staying part of a particular community. That's not making them give up, it's making them try to hold on to the few remaining pieces of the culture as hard as they can. And if all they need to do is get a few judges to switch their votes, that's a winnable fight so they might as well keep at it.
The only way we can complete the transition from a community-based culture to one that maximizes the freedom of individuals is to settle the issues, not keep them under debate forever (no matter how addicted politicians are to NARAL/ProLifeAmerica donations). Right now there's more institutions being torn down than built up, and that's leaving a lot of people in a bad situation. We need to find ways to build new communities that support children and relationships. We can't do that while the culture war drags on forever.