Model years can start production anytime between May through Sept ('06 vette ran through Sept of this year). As for the diesel, remember I did qualify this. However, this information not only comes from people I know, but it was on GM drive time, which is a video we can tap into. It is not secret if on GM drivetime.
And on this video, they stated that they are considering bringing the diesel to the states.
US demographics are quickly changing and GM will have to go with the flow.
As for a V8...I can't say, but be patient, but don't expect a Hemi. The Hummer is designed for off-road, and not for 0-60 times to and from the soccer field.
