I don't how anyone could have voted for Obama thinking he would leave gun rights alone. Of course he left them alone in his first term, as his first term partially involved running for a second term. With the second term, he has no further re-election to worry about. And he is a committed ideologue.
I also would have to disagree that he is not going to push hard for this. His administration is already planning a state-by-state effort to try to convince legislators to support his gun control agenda.