If not, then not. DC ban stays put, they weasel an opinion to cover their asses, and a bunch of fringe "gun nuts" start "voting from the roof tops" as new gun control legislation is penned in half the States in the Union.
"Fringe," you say?
Only if the Founders, including the Second President of the United States, were "fringe."
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants." - Thomas Jefferson
But there's no real point in worrying about that, as given the long history of the Supreme Court's discussion of the Second Amendment, it's extremely unlikely that your scenario will come to pass.
Actually, some of the State Constitutions make it clear that the right to keep and bear arms is an individual right and includes the right to use those arms for self defense. Maybe those are the half that will not write new legislation.