Things to ponder:
1. What is the legal nature of the result of an initiative under California law with respect to a court's ability to overturn it? It seems to be more than statutory, but less than constitutional. At any rate, it's a somewhat unique creature.
2. If the measure is effectively a constitutional amendment, as Prop 8 opponents argue, doesn't that also argue against it being overturned by the state supreme court? Constitutional amendments can be used to override court rulings - see the 11th Amendment, the 13th Amendment, the 16th Amendment, etc. in United States constitutional law. Still, there is likely less process employed in getting an initiative passed - making it easier to impact rights than with the process required of a constitutional amendment - and that could be the sticking point.
3. Does overturning the ruling of the State Supreme Court that permitted gay marriage in the state require a lower bar than a constitutional amendment because the right to same-sex marriage is not actually enumerated explicitly in the text of the state constitution?
4. Will the court consider prudential concerns involved - namely the risk to its reputation - in overturning a plebiscite supported by 52% of the voting citizens of the state on a matter of heated moral controversy? But one that involves individual rights...
5. If gay marriage proponents continue to embrace the idea of overturning Prop 8 via the judiciary, will the move backfire if the court ultimately agrees? Will it cause, as the illegal granting of gay marriage licenses did several years ago, increased hostility to gay marriage by some parts of society - not to mention further legal and legislative retrenchment across the country?
Personally, to achieve some permanence, I think the best move for the gay rights movement in California would be to admit short-term defeat in the Prop 8 battle. It should refrain from overtly wielding the courts as weapons. But it should recognize the encouragingly slim margin - and move on to a push for a full-blown constitutional amendment that positively enshrines the right to gay marriage - or some more beneficial conception of marriage - in the state constitution. Then get it passed in 2010 (or the next possible election given whatever timelines are in play). That's a positive action that follows an established, evolutionary, law-making process, as opposed to a quick, revolutionary, judicial revision. That's probably not satisfactory or just in the eyes of many, but that's when things would truly achieve some sense of legal and political normalcy.
Perhaps that's the Booker T. Washington approach to the social/cultural/moral issue (as opposed to the W.E.B. DuBois), but I think it's the sound approach if a group wants to win the war, not just some battles.
Rebuilding the clock takes longer, but it's the only way to stop the pendulum from swinging. Or at least from wrenching back and forth excessively.