To explain for those of you who are new to the concept, the Bill of Rights was originally read as applying only to the federal government. Starting with the takings clause in 1897, the Supreme Court has interpreted the Fourteenth Amendment's due process clause as "incorporating" some of the provisions of the Bill of Rights against the federal government. In the famous words of Benjamin Cardozo, the Court deems rights to be incorporated against the states if the given right is seen as being "implicit in the concept of ordered liberty." Strictly speaking -- and as the Court first interpreted the requirement -- the Second Amendment may not seem to meet this standard, as plenty of liberal democracies do not recognize an individual right to bear arms. But, of course, one can say the same thing about many of the provisions of the Bill of Rights that have been incorporated for decades. The Second Amendment is the last major provision not to be incorporated, and under current standards the case is relatively easy.
The only question is whether some liberal justices, while continuing to disagree with the expanded reading of the Second Amendment announced in Heller, will concede that the Second Amendment should apply to the states as well as the federal government. The tone of the questions would seem to suggest that this could be another 5-4 case. But certainly there can be little question that states as well as the federal government will not be permitted to ban handguns outright, with the winning margin being the only open question.