Well, the only thing the Federal legislatures could do is pass a law saying States didn't have to honor another state's same sex marriage contract or that the Federal Government didn't have to acknowledge them.
They did that, and a Federal Court has found that unconstitutional.
The only other Federal level action would be if the Supreme Court ruled that all people had a right to marriage, same sex or not. I don't think their are any cases working their way toward the SC on that basis. But I could be wrong.
I think for the present you'll see them require states to respect same sex marriage contracts from other states.