I dont think it's a mock up, the subject was brought up just last week with GM. But for sure it's not scheduled for release before end 2008, which is about the same year Land Rover Freelander is scheduled for a complete remake.
The H4 is to compete with the Freelander, BMW X3, Toyota RAV4, Nissan Murano and the new Volvo XC-50.
Gm is contemplating at a platform based on the Chevy Equinox. Personally I dont favor the idea, coz the smaller the vehicle the less offroad capable it becomes due to smaller components, of course lesser weight plays a + role, but still, a unibody on a Hummer ? naaaah. that would disrupt the entire Hummer Image.
What's next ? a Hummer Quad ? still I dont want to speculate, didnt the H3 receive bad vibe before it came out? yet now it's the most talked about Hummer, in a positive way.
Maybe that's what's upsetting the H1 guys

the H3 stole all the limelight so far

. give it time guys it will even off
SledgeHummer