Z28 is an RPO code... that is it is for production cars. ZL1 was a COPO code, that is extremely limited special edition.
The new car is using an LSA which is a normal production motor. It is not limited production or a special edition. It is simply a faster car built off the basis of an SS. That was essentially what the Z28 designation stood for traditionally.
If they do a limited run high output version, analogous to the KR and supersnake, perhaps with an LS9 then maybe the designation ZL1 would qualify. However as the ZL1 was essentially an engine code it will probably be uses on a Corvette before it trickles down to the Camaro.
On a side note I believe that Z28 was simply a trim code in the 90s. B4C Camaros had essentially the same drivelines as the other v8 cars but did not have the Z28 RPO code, which all the cars including the SS carried. The B4C had very different trim and other minor differences.
The only other recent code that comes to mind for a high performance Camaro is 1LE which is more a weight loss and track pack than luxury and horsepower package.
