A challenge to section 3 of DOMA has made it to the Supreme Court and the Supreme Court may take it up and rule on it next term. Section 3 defines marriage for purposes of federal law.

Section 2 (specifying that the full faith and credit clause does not apply to same-sex marriage), which Law Prof Andrew Koppelman suggests is roughly as effective as a ban on hunting unicorns is not before the court and if Koppelman is right (and the section does nothing anyway), will never be before the court.

My prediction is that they will, and they will strike down this provision on the grounds that defining marriage has been a traditional role of state governments and that the federal government must defer to the states as to who is married and who can be married. They would then hold that there is no valid reason for the federal government to treat these differently. This decision is likely to be 7-1, 8-1, or 9-0 depending on whether Scalia dissents and whether Kagan recuses herself.

The result will be that it will fully revert to a state-by-state approach and that if you are in a state which recognizes same-sex marriage you can bring your same-sex spouse over, but if you are a resident of a state which does not, you may not.