It's unclear, after Lawrence, what the court would do with Prop 8.  It is clear that at least four votes (Alito, Scalia, Thomas, and Roberts) will vote to sustain it.  The question will be, for the state--tactically--can you swing Kennedy?  I doubt it, especially given the strong state interest in defining marriage .  And if you were going to do it, how would you do so?  Indeed, could you even swing Souter and Breyer? 

The chances that this particular Court will vote to affirm prop 8 are excellent, which means that if you are a conservative, the timing of the lawsuit is also excellent. The tide of public opinion is against you.  Were a majority of states to adopt a gay marriage statute, part of the predicate foundation for finding a substantive due process would be laid.  Now, in contrast, gay marriage is a minority position and one that is relatively recently adopted.  Furthermore, if a liberty interest were found in same-sex marriage, the pathway to non-discrimination statutes and case law that bans discrimination based on sexual orientation is fairly straightforward.  That such a statute is both morally and economically desireable is beside the point.  It means that the baptist church can't fire its gay receptionist (which means, of course, that the parish cat will have to defend its honor).  

 I would also note that Sotomayor's nomination makes no difference.  The Republicans know this, and this fight is a warmup.  The only people on TV and in the media are the B-team.  (Pat Buchanan?  Seriously?  Who cares?)  The voting patterns on the big cases will not be changed by Sotomayor's nomination: Boumedine would still be 5-4. Even Stevens' retirement would only preserve the status quo.  The fight will come if--and when--one of the conservatives retires.  That is the point at which the makeup of the court may drastically change.  Barring anything bad coming out at the hearings, the Republicans, except Sessions (R-Rock Ridge), are going to run from this fight.

If I were the right wing, what I would be truly scared of is a former politician, like O'Connor, or Brennan, or Warren, that was nominated.  There is no more important (and less observed) rule in American law than the law is what five people think it is.  A person that knows how to build consensus on such issues is much more of a danger to their vision of judicial hegemony than a predictable liberal vote.