Yes, but it's not being constitutional doesn't mean it will be ruled un-constitutional. The Court was 9-0 on the issue in DC v Heller regarding whether or not the Second Amendment protects an individual right to keep and bear arms, yet four of the justices still claimed the Washington, D.C. gun ban was constitutional essentially because, as they saw it, the Second Amendment no longer applied in modern society. So the ruling was 5-4 in that sense. And it was 5-4 in Chicago.
On the NY ban, provided none of the conservative justices dies any time soon (as they are getting old), it might get ruled 5-4 on the hand gun issue, but on the AR-15 aspect, which IMO is blantantly un-Constitutional as the ruling in DC v Heller specifically said that the word "arms" in the Second Amendment protects weapons in common usage among the citizens (which would include the AR-15 in particular, which also has nothing special about it as far as guns go), I think it would be a long-shot.
I could very much imagine a 5-4 ruling in which the magazine limitation part of the law is shot down as it bans too many hand guns, but where they uphold the AR-15 ban part of the law, unless the lawyers arguing the case are smart enough to point out that the AR-15 part of the ban is also un-Constitutional as well. I have lost some faith in the gun rights community though after watching the hearings on Capitol Hill recently where it seems even a lot of the gun rights people (LaPierre for example) seem to lack basic knowledge about how to defend the AR-15.