You know, this already happened in New York city. First they had everyone register the "evil" guns, promising - of course - that the lists would never be for confiscation. Then, some years later they banned all the semi-auto rifles and cops actually went door-to-door making sure all those guns were out of the city.
There is no reason they couldn't try this if they have support in both the House and the Senate.
"Gun control is the idea that a woman who is brutally raped and killed is somehow morally superior to the woman who shoots her attacker."