Prop 8 - Majority decision holding the Petitioners lacked standing, resulting in the
DOMA - Fractured opinion striking down DOMA with the four-Justice liberal bloc holding that it violates a right to same-sex marriage and Justice Kennedy (who I predict will pick up a buddy or two) holding that it violates federalism principles (there will probably also be some votes for SCOTUS lacking the authority to hear the case because Obama wouldn't defend it - even though he enforces it. A group of GOP representatives did defend it, but it's questionable whether that's good enough because they're not a real party in the case).
The end result being that there is still no Supreme Court precedent on a right to same-sex marriage . . . but Prop 8 and DOMA both get struck down.