Those interested in owning a gun legally would still be able to do so and would, perhaps, be persuaded to take greater care to prevent those weapons from being misused. Those who should never own a gun, those who misunderstand the danger that owning a gun poses or who would seek one with intent to harm, would find fewer easy opportunities to do so.
The gun industry would have to make adjustments, but given that a broad market for guns would still exist, dedicated manufacturers like Smith & Wesson (SWHC) and Sturm, Ruger (RGR) should be fine. More diversified retailers that happen to sell guns, like Wal-Mart (WMT) and Cabela's ( CAB), will barely feel the pinch.
I'll say it again: Change the culture. It can be done and it should be done.