Scalia may be telegraphing that SCOTUS passes [for now] on a gay marriage decision.
SCOTUS may decide that each state is allowed to set its rules for marriage. That being said, SCOTUS may invalidate DOMA due to the 14th Amendment Equal Protection Clause and the Full Faith and Credit Clause.
Then, in the other case, SCOTUS may decide that the concept of gay marriage is so new that it is too soon to rule on it. Given that only 12 of 50 states have adopted it.
Therefore, SCOTUS may vacate the 9th Circuit’s ruling that Prop 8 is unconstitutional [at least for now] - citing that each state can decide its own marriage rules. And that Prop 8 was constituionally approved by CA voters.
“Given that only 12 of 50 states have adopted it”
How many of those states by an actual vote of the people. In most states that have “adopted it”, a liberal state legislature passed it and an Obama-loving liberal governor signed off on it.