production is limited because this is pretty much an all out race car with a VIN that you can drive on the street.
Most people will not want it and to those people the ZL1 will be cheaper/nicer of an all around car they are looking for.
The Z/28 is either destined for a carcover and garage or the race track.
So I believe the production will be limited but something tells me a few thousand of these cars will be made. They sold plenty of 70k+ Corvettes why not sell that many Camaros?