As more states arrive at marriage equality, whether through the courts, legislatures, or ballot box, the number of states with neither equality or a state constitutional amendment forbidding equality have almost all left to the ends of the continuum. Indiana looks set to pass a state constitutional amendment banning same-sex marriages, which will leave only Pennsylvania, West Virginia and Wyoming in this limbo (all three states, and Indiana, do have laws defining marriage as between one man and one woman).
The campaigns for marriage equality have achieved surprising successes over the last decade, but moving forward, winning equality through the legislatures and state referenda will be more difficult, since repealing a constitutional amendment is typically a difficult fight. Most or all state supreme courts are bound by the state constitution, which will make action by them difficult. This will leave only the federal judiciary and U.S. Supreme Court to expand equality further.
Note: Yes, Utah briefly had marriage equality, but since the U.S. Supreme Court granted a stay on the lower court’s ruling, I’m counting their constitutional amendment as still in force.