I would belive that SCOTUS will/should just send it back to the lower court saying you got it wrong (as they did with the tazzer ban) This means that it is not a national/historic ruling that can be cited as case law.
the reason i belive this is becasue of the Heller decision.
"(f) None of the Court’s precedents forecloses the Court’s interpretation. Neither United States v. Cruikshank, 92 U. S. 542 , nor Presser v. Illinois, 116 U. S. 252 , refutes the individual-rights interpretation. United States v. Miller, 307 U. S. 174 , does not limit the right to keep and bear arms to militia purposes, but rather limits the type of weapon to which the right applies to those used by the militia, i.e., those in common use for lawful purposes.
2. Like most rights, the Second Amendment right is not unlimited.It is not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose: For example, concealed weapons prohibitions have been upheld under the Amendment or state analogues. The Court’s opinion should not be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms. Miller’s holding that the sorts of weapons protected are those “in common use at the time” finds support in the historical tradition of prohibiting the carrying of dangerous and unusual weapons. "
The basic reading of this is YES states can ban guns that are considered dangerous or unusual. BUT they can not ban gun (such as handguns) that are in common use. I believe that because AR 15 style or AK style rifles are in common use (There are literally millions of them) making them in common use, AND because they are not any more dangerous then other types of (featureless) rifles NOR do they equate for a sustaial amount of firearms used in crime, They are not and can not be designated as dangerous weapons.
So as with tasers i believe SCOTUS will have no choice but to send it back to the lower court to rethink their stance heance making it only applicable in that circuit OR they will have to hear it in open court and have no choice but to say they are constitutionally protected (the only other option would be to overturn Heller in which case here comes the second civil war.)