Basically, as I understand it, and I may of course be wrong... DOMA is an "easy" choice because it's only about the federal government's power. DOMA interferes with states rights to regulate something, and it is fairly neutral against states that have bans against same sex marriage. I can see the conservative hawks agreeing that it is an unacceptable federal intrusion into states rights.
Now Prop 8 is another kettle of fish, because if the court agrees that prop 8 is unconstitutional, then it invalidates all the same-sex marriage bans in all the fifty states. I could see the conservative hawks being all over that one.
I also don't trust the geriatric leftists on the court, because remember it was the 1990s democrats that gave us the perversions called DOMA and DADT. I'm not sure about them either, and I could well see that a majority could vote to uphold the constitutionality.
As I said before, I'd like to see a few replacement on the court before Prop 8 was handled. Institutionally though, I understand that there's a time limit.