A few observations:

1. This decision is based solely on the California Constitution. Within the federal system, the California Supreme Court's view of the meaning of the California Constitution is final, and the U.S. Supreme Court has no jurisdiction to revisit it. So there can be no federal review of the question whether Prop. 8 violates the California Constitution.

2. Supporters of same-sex marriage rights can of course argue to the U.S. Supreme Court that the U.S. Constitution mandates recognition of same-sex marriage, in all states and under federal law. But it seems unlikely that the Court would accept such an argument at this point, and in any case this case is not a good vehicle for that, since the decision below was all about the California Constitution. (I'm not sure that federal constitutional arguments were even made by the challengers, but in any case they weren't considered by the Court.)

3. Supporters of same-sex marriage rights can also argue that the Full Faith and Credit Clause requires recognition of out-of-state same-sex marriages, both in California and elsewhere. I'm not an expert on the subject, but I my sense is that this argument will fail, at least before the current U.S. Supreme Court and probably also before many state and federal courts (at least ones that aren't willing to find a constitutional right to same-sex marriage in the first place).

4. Finally, supporters of same-sex marriage rights can also try to put on the ballot an amendment that would repeal Prop. 8, and would amend the California Constitution to actually recognize a right to same-sex marriage (or to authorize the normal legislative process to enact legislation recognizing such a right). My sense is that such a proposal will indeed soon pass, perhaps not in the next election cycle but likely within the next 10 to 15 years, if I'm reading social trends correctly.