As recently as last week, U.S. Supreme Court Justice Ruth Bader Ginsburg was nonchalantly dismissing the need for the court to weigh in on marriage. Because lower federal courts are all in agreement that marriage bans are unconstitutional, she explained, there's no need for the justices to intercede.
But that may (or may not) change now that a judge in Puerto Rico has upheld a marriage ban. Puerto Rico is part of the First Circuit Court of Appeals, along with several New England states, which means that the case could work its way up to the U.S. Supreme Court. If the First Circuit upholds the Puerto Rico ruling, the Supreme Court could have great interest in settling the dispute.
That's a pretty big "if," though. The plaintiffs in the Puerto Rico case are highly likely to appeal the decision, and the First Circuit is highly likely to reverse it. All the other states in that circuit have had marriage equality for years, and the Puerto Rico judge's decision is way out of step with modern interpretations of constitutional law.
The Puerto Rico case joins ongoing litigation in the Fifth and Sixth Circuits, both of which could issue decisions very soon on marriage equality. It's possible (though unlikely) that those courts could uphold marriage bans, in which case the U.S. Supreme Court would have yet another opportunity to weigh in.
Although marriage equality seems inevitable at this point, there's no telling how many more unexpected obstacles could pop up.