I'd guess the production Grand Am replacement would be on the Auto Show circuit this winter, since it's comming out soon, as would be the C6 Corvette, the STS, the new Buick Regal, the H3, the Cavalier replacement (at least in concept form), some new display of a Solstice based car, and some new Cadillac concept (they seem to have a showstopper every year), and some version of an upcomming RWD sedan.

That's just starters.

 

GTP4/GTP6 -- too many letters before the series number. G4, G6, G8 are fine, but ideally you'd want the first letter to represent the series/car.

Food for thought: Perhaps the G6 is the "M" version of the Grand Am (reports are that they are targetting BMW). Will Pontiac use numerical names like 628, 636 etc?