Actually, all (Federal) Circuit Courts of Appeals have 10 members, though a 3 judge panel from the 10 usually hears an appeal first, as in this case. While it could go straight to the SCOTUS, that usually happens only where a deadline has 2B met.
And politically, I'll bet Obama does not want a Supreme Court fight on this B4 the election. As it is, he'll have the healthcare mandate case there this year, and a confirmation fight if (I'd guess Clinton appointee Ruth Bader Ginsburg) retires in June.
In terms of the effect of a 2-1 appelate panel decision on anything "The Supremes" might rule nationally, its minimal. It can't be presumed that other state courts would ovaride referenda in their states on this issue, and I doubt the Supreme Court would go further than "civil union with all the rights married couples get".