While this is a Great Day for the advocacy of 2A activism, let's not go further than we have to ... Which is exactly what Judge Posner did in writing his decision.
Alan Gura has already indicated that he will be/is writing a petition for certiorari to the Supreme Court in Kachalsky. This will add a small amount of justification for the Court to grant that cert.
There will be Rule 28J letters submitted to Peterson (CA10); Woollard (CA4); Piszczatoski (CA3); and the trio of cases at CA9 - Baker, Peruta and Richards. A 28J letter is a submission of Supplemental Authority to the court after briefing is concluded, before or after oral arguments have been made. This decision, while not binding precedent in any other circuit, it is persuasive authority in all other circuits.
Judge Posner was careful (I have only scanned the opinion, as yet) to not say that the CA2 (Kachalsky) was wholly wrong. Please note that. Because it means that IL may in fact pass a similar set of laws as NY.
In that respect, this is not a circuit split. Yet, some of the language by Judge Posner, may go a long way towards getting "may issue" laws ruled as unconstitutional.
So while there is much to rejoice, I would also caution restraint.
I will have more to say, when I get off work and have had time to digest this decision.