To me its pretty obvious that the Z28 will be coming but not just yet.
It's not like the 80's and 90's when they gave it a few extra HP and put bigger stickers on the car. The new Camaro is RETRO etc.
So.........
They will make a few special packages however they see fit but the Z28 I'm sure will be very special.
I'm willing to bet they will wait for that newer 5.5 V8 or something and then call it a Z28 like they did with the 302's when the 350's were the big dog on the porch.
My feeble 2 cents...
-bobby