A consensus seems to be emerging about what happens next to an opinion that is being widely characterized as a narrow decision tailored to appeal to the sensibilities of one jurist -- Justice Anthony Kennedy. Eugene Volokh's view is typical:
This is going up to the Supreme Court. I suspect that the backers of Prop. 8 won’t even ask for en banc review by the Ninth Circuit, since they’re unlikely to win there. Depending on how quickly they file their petition for certiorari, the Court will either decide in late September to hear the case, or will decide this late this Spring. Either way, the Court will hear the case next Term, though probably not before the election. Though, for reasons I describe below, the decision only applies to states, like California, that recognized civil unions but not same-sex marriages, it’s still a conclusion of national importance, one on which the Supreme Court is likely want to speak. And even if, as described below, the decision is limited just to California, I think the Court will still think it’s important for it to resolve the question.
But at least one voice thinks the Court may shy away from taking it on:
This situation applies only to California, and has no bearing whatsoever in any other court case anywhere else. Judges working other cases are very unlikely to find anything in this ruling which applies to their cases. And when you think about it, that statement can apply to Supreme Court judges as well. Unless they’re just itching for controversy, it would be very easy for them to point out that there are no burning questions of national importance which require their attention. This decision appears tailor-made to allow the Supreme Court to duck this case altogether.