Under the 1968 GCA, Federal Law prohibited anyone from purchasing a pistol from out of State. rifle and shotgun purchases were limited to contiguous States.
Under the 1986 FOPA, the limitation on rifle and shotgun was repealed. However, many States had passed their own version of the 1968 GCA laws. When the FOPA went in effect, some States immediately repealed their rifle and shotgun bans. Some took a few years to do so. There are still quite a few States that have this law in effect.
If this lawsuit prevails on its merits, people will be free to purchase handguns from an FFL in any State, provided that the sale is lawful in both the State of the seller and the buyer. In other words, the federal ban on handgun purchases being restricted to your State of residence will be ruled unconstitutional. The law in VA will be struck, as VA is a party to the the lawsuit.
If the 4th Circuit agrees with Alan Gura's arguments and strikes the federal law, then that law (the federal law) is stricken throughout the entire US. The only State law that this will affect is the mirror law of VA (as they are a party to the suit and their mirror law is specifically targeted in this litigation).
However this case turns out (for or against us), it will be appealed to the Supreme Court.
Should this suit survive the SCOTUS challenge, then it will be a matter of litigating in the individual states. With the federal precedent being set that these laws infringe the core right, it shouldn't be too long a battle.