I wouldnt go that far on saying that the G8 wont come out....well, not on the W body.
With the Hamtrack plant, in where they make the Caddy DTS, Buick LeSaber, and Pontiac Bonnie, is moving to something else..*cough*zeta*cough* and one of teh 3 Oshawa plants are going to Zeta, Both teh W body, and the moddified G body(what the DTS/Bonnie/Saber is on) are out the door. Pontiac will go to an almost all RWD or AWD chassis set up to stay with its performance image. There is even news that Kappa will support a RWD, Ecotec powerd coupe. The news is so good, that Car and Driver quoted GMI on it! 8)
Pontiac WILL offer a RWD/AWD sedan on Zeta, and so far the name will be G8 as Pontiac gets away from naming cars. That, I can say 100% that Pontiac will have a RWD/AWD sedan, as well as the GTO built off Zeta.
The Zeta coupes will be first, as for some reason the news is GM is moving up the release date to the Zeta coupes for 07...hrmm who knows why?
67...07...67...07...Someone say birthday?
Anyway, the G8 as you saw it in the Autoshow wont happen, but there is a good chance that he RWD/AWD sedan will be called G8. The Pontiac Bonnie GXP is more of a place filler till the Zeta sedan hits the market.