Marc Fischer, a local columnist for the Washington Post, has a column on the Supreme Court's taking of the appeal by DC of the Second Amendment decision. For what it's worth (nothing), I agree with his take--the court's going to decide that DC can't ban handguns but can regulate them. Which is about where we ought to end up. If we can take car keys away from senior citizens who can't drive safely, we can (and should) also take guns away from people who can't shoot safely.
I'd treat guns like cars. Every American, even including illegal immigrants, has the right to drive a car, once they've been tested.