I think people will, as they have done for many years, pay the extra just to have the V8. Yes, the XR6T is quick and a really good engine, but it's still 'just a six'.
The after market potential for the V8 (as with the turbo) is also yet to be seen. Looking at the specs of these new engines, i would say it would be huge. Imagine, a slight increase in capacity, say 5.8 or so, and some forced induction. Potentially Viper territory there.