Not nessecarily, and just because you have done a product rollout doesn't mean you don't start from square one when you want to make an upgrade.
A car of this type really isn't the generic cookie cutter variety.
It is expensive to make a new new car. Now add to that you have an enthusiastic target audience that won't hesitate to shove its foot in its mouth to tell you to pound sand if the Car isn't 110% what they envisioned.
I can guarantee out of the gate GM had the base LS (LT is an upgrade to the LS) and SS in mind based on their existing lineup. 2 main packages that you can then trim out keeps cost down and your reach broad.
Hell when the Camaro debued the LS2 was the hotshit engine.
Contrary to popular opinion the LS7 was only ever a Camaro pipe dream - GM has said on more than one occasion it was hella expensive to manufacture.
During the following years GM has had to adjust to market feedback, Govt and envirionmental pressures and its fanbase to develop the Car we see.
Don't think you can just say alright take what you saw and extrapolate and give me a 3rd model. First GM has to see a return on its investment before putting more money into a new option pack.
That being the case it is of no benefit to annouce anything now for a product that may not exist if the market won't bear it. All that will create is bad press and ill will in the fan base for announcing and shelving a product.