So if you get 60 days advance notice to renew your card and it takes 90 days to get the card, are you in violation of Illinois law to own a gun during the gap and subject to state reprisal (prosecution)?
I have no idea. I’m far away.
If state law specifies that the state is required to issue the card within 30 days of receiving a valid application, then although the statute does not specify a specific penalty for the state's failure to issue the card in timely fashion, the fact that an individual does not have a current FOID card on their possession would be purely a consequence of the state's unlawful failure to supply it. As such, prosecuting someone for the state's unlawful activity would constitute entrapment. That's not to say the state wouldn't try it and impose considerably legal expenses upon its victims, but that wouldn't make the state's actions even remotely valid even outside the RKBA issues.
Another thing to note is that unless things have changed, the statutes that require a FOID to acquire firearm or ammunition, or to transport an assembled firearm on a public right of way, specify that the FOID has to be current and unexpired, but, the statute that requires a FOID to possess a firearm on one's own property merely specifies that the FOID must have been previously issued by the Illinois State Police. Under an honest reading of the statutes, someone whose FOID expires would--unless or until it is renewed--not be allowed to purchase firearms or ammunition, nor transport firearms that were assembled, but would not be committing any crime merely by having the firearms on his own property, or by transporting them in a broken-down (disassembled) condition.
Technically, yes you are. Mayor Daley had the State Police notify the Chicago PD when a city resident FOID expired. They then got a knock on the door asking for their firearms.