The hardest part will be if GM just makes 3 sedans here. Then they will be forced into the game of differentiating the products sufficiently so that Cadillac remains the top choice.
my prediction is GM is already in that trap.
now if the Camaro is a coupe or coupe-like then I can see powertrain overlap.
but GM will not have a performance Chevy for $40,000 less than a Cadillac V or V Blackwing with near equal, powertrains.. if they do that will be bad for Cadillac.