National CCW reciprocity is in the works, although I'm not sure how good of a chance it has in passing. Opponents will argue that it is unfair to force states to accept the laws of another state. But this is already an accepted practice with things like marriage licences and driver's licenses. Imagine if you had conditions on your motor vehicle where you could only legally drive it in certain states. (And the states don't necessarily border each other.)

The contract clause of the Constitution requires states: "No State shall. . .pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts...". Proponents of gay marriage want to use it to recognize marriage contracts from other states. It's a long shot, but if they are successful it could pave the way for gun owners as well.