If they do well enough (and I think they will), they'd be wise bring over the smaller engines within a couple years.
That said, it's ripe for dealer markup, and they're saying they'll allow it.
What I think will happen is the SS will start between $45k-$50k, which is about $15k less than the CTSV. I think they'll be able to sell all they make is it does hit that price... there is a market for it.
If it does get higher, around $55k-$60k, then that's going to be a hard choice (for those that can afford to pay that much for a Chevy) between Chevy or CTS\V... and I know what most of your smarter/discernable buyers would choose.