I dunno, just as you dunno, how the Supreme Court will rule on the matter of Gay Marriage. I see its opponents everywhere throwing in towels and conceding its inevitability so you might expect that even Scalia and Thomas would figure "What's the point?" and vote for it, if only to make their righter-wing decrees seem more reasonable. If they want to say, "We don't always vote against minorities," this might be a good time to do that. Then again, you'd also figure Scalia would see some value in not making it clear on most issues that he has his mind set in concrete well before the oral arguments.
Then again, the Field Poll in California, which is the poll always cited on this topic, now says that denizens of my state support by a margin of almost two-to-one, the right of gay couples to wed. That's enough that if a measure went on the ballot to allow it, I would think its opponents would have a hard time raising funds or generating outrage to defeat it. Then again, some folks have pocketed a lot of money and also manipulated votes on other matters by panicking some voters into thinking the world will end if Gay Marriage is not defeated…so someone will try it.
Then again, they won't win. This battle is over.