In the most recent issue of Chevy Hi-Performace magazine, the magazine claims that not only is the LS3 going to be used, but that more info states there should be a supercharged version.
On the V8 table now is an LS3 engine with L92 cylinder heads. This engine will be installed in the Z28 and produce in the neighborhood of 400-450 horses. Additionally, there is talk about a supercharged 550hp Z28 engine with a Roots-style blower.

I'm all over the supercharged LS3!!!! or wait until 09 for the SS with the LS7!!!

If they do put that supercharge V8 out; it will be it will be the hottest stock V8 out. This is definitely going to start a war. I love it.