Not yet. This ruling only applies to the District of Columbia. The D.C. Court of Appeals is the equivalent of a state supreme court.
Except for that tiny fact that the judges on that court are all hand-selected by the President of the United States.
I think that's why they call this court 'Supreme Court, Jr.'.
Are there any USSC justices that served on the DC Court of Appeals, to your knowledge?
While you're correct that this won't have any effect on state gun laws, the DC Circuit is much more than the equivalent of a state supreme court. Its rulings have an effect on DC obviously, but it also decides many cases arising out of federal agencies and their huge power. Because the federal agencies and government have power throughout the land, it is considered the most important Circuit Court in the nation. Decisons made there often do impact the entire country.
It's a bit more than that. First of all it's a federal court. Second it's on the same level as the other numbered circuit courts of appeal, where it is often considered "First among equals".
Because this is a DC law that is being challenged, it just means that it's federal case from the beginning, since Congress has exclusive legislative jurisdiction over the district, even if they delegated some of that to the DC city council. That means that it's a clear cut case of what the second amendment means, with no intervening question of whether it applies to state government infringements.