To extend the ruling beyond the DC circuit. Most of us don't live in DC.
If the Supreme Court agrees with the DC circuit, then that strict scrutiny test must be applied to, at a minimum, all federal laws which infringe upon the right, that is all federal gun control laws. If they agree that it's fundamental right, then that probably extends the protection against infringement to the states under the current "rules" of application of the 14th amendment. Keeping in mind that the U.S. Supreme Court likes to keep their decisions as narrow as possible, what are you expecting them to add to the DC Circuit Court's generous decision?
Not expecting them to add anything, just extend the precedent to all the districts, not just DC.
Meaning that A) state laws must conform to the second amendment (as, for example, state laws must conform to the first amendment) and B) the second amendment means what 5 justices on the U.S. Supreme Court say it means. The U.S. Supreme Court will now decide, for all 50 states, the definition of "arms", the definition of "to keep" and the definition of "to bear".
You want that. You want those unelected and unaccountable yahoos, those who gave us abortion, sodomy, Kelo, nude dancing, freedom from religion, asset forfeiture, no-knock, flag burning, etc. to define our gun rights and make that definition applicable to all 50 states. This is a good thing, in your opinion.
You may get your wish.