A supreme court decision is expected at the end of this month.
Only a decision on
whether the Supreme Court will hear the case at all -- in technical terms, whether the Court will grant certiorari.
If the Supreme Court decides not to hear the case, then the decision of the U.S. Court of Appeals for the D.C. Circuit striking down the DC gun ban stands as law in that jurisdiction. (And a zillion suits will then promptly be filed in the DC federal trial court, challenging various ATF regulations as 2A violations.)
If the Supremes do decide to hear the case, then, over the next few months, the parties will file a new set of briefs on the merits (and there will also be roughly eight zillion "friend of the court," a.k.a.
amicus curiae briefs, filed by the NRA, SAF, Brady, the various States, etc.). The Court will then hear oral argument early next year, and the Court's decision on the merits will be handed down probably in late June 2008.