You realize that for a ban to happen it has to pass through the house. Republicans control the house. Feinstein is putting her bill up to grandstand, and then when it fails she can parade around and say how hard she tried. Obama can't force this through even if he wants to. Executive orders don't apply to this kind of thing. Let's also not forget most Americans have a very short memory. All the rah-rah ban gun talk dissipates by the day. Also LOL @ blaming the NRA. No matter what they said or didn't say will have little effect on how the house votes. People voting for/against already knew where they stood before the press conference.
Let's also not forgot a lot of Democrat house members won their seats by small margins in independent states. Voting for a ban is going to hurt come reelection time if you live in say.. Ohio. Or other states that have a large amount of gun owners.