how does that streangthen the RKBA advocates position on a federal level or is this to be taken as a purely state level win?
This is interpretation of the Second Amendment of the United States of America.
1) The State of Illinois appeals
2) SCOTUS hears the case and overturns the CA7's opinion -
This is the law of the land. Again, this is the United States - not the State of Illinois, it is much more than a state level win.
IMO, anti gunners are hoping that IL does not appeal. IMO it would be a tactical disaster for the gun control movement to appeal it.
As to how does it affect national RTKBA, well very little IMO. It would prevent the federal government from enacting the type of ban that Illinois had in place, but to the best of my knowledge the federal government has never come close to enacting a law like that and IMO - would not have enacted a ban on carrying, at least not in my lifetime. And even if they tried, there is the issue of states rights. I'm sure Texas and quite a few other would fight any federal ban on carry.