It won't be limited in the sense that 'we shall only build 280 units and stop there' type of limit. But there is no way they can build 28,000 of them either. Too many logistical issues get in the way.
Also, I don't believe the engines are 'left overs' from Wixom. There are differences between the Z/28 LS7 and the one in the Z06, namely the A/C being optional. Even though its a slight change, I can't see them running around pulling apart the front end of the engine to remove A/C and swap in a dummy pulley every time a Z/28 gets ordered.
Note, if I've gotten any facts wrong in the above, just ignore any points I made with them
don't believe a thing you read about the next gen Camaro -- as history has proven time and time again:
WE DO NOT TALK ABOUT FUTURE PRODUCT PLANS PERIOD FbodFather
Camaro5 Fest sub-forum