It's not that clear-cut. The 2-1 ruling, while very favorable to our cause, applies only to California, not even to the entire territory covered by the Ninth Circuit. That's because the ruling declares it unconstitutional to take away the right to marry, which gay Californians enjoyed.
On one side, that's bad: the 9th didn't rule that there was a Federal right to gay marriage, which means that all other 49 States (minus the ones that already have gay marriage) have to wait.
On the other side, that's good: as long as the ruling affects only California, I doubt that the Supreme Court will want to get involved. They certainly don't want to be the Justices that created a Constitutional right to gay marriage. But they know which way the wind is blowing, and they don't want to be forever remembered as the last hurrah of homophobia (Dred Scott, anyone?)
If I were inclined to bet, I'd say that Prop 8 supporters should be going for a full hearing, hoping for a different ruling with which to go to the Supreme Court. If that doesn't happen (not likely to happen), then the Supreme Court will not grant certiorari and gay marriages can begin.
I love the way the judicial system is playing it. It's an interesting chess game: Judge Walker with the opening gambit, then the panel with an interesting twist. It's judicial drama, and we are on the winning side!