[CadiEldo67]

Well, if GM is willing to admit that this setup is indeed working, then Pontiac and Buick need to fill in the gaps for each other, and GMC only worries about GMC. For example:
Pontiac has a Solstice(and I would give them the sedan version of the Astra with Solstice styling), Alpha G6, (hopefully Grand Prix) and a G8 (Bonneville), with coupe versions of the GP/Bonnie being the Firebird and GTO, respectively. So that leaves Buick room for a Delta II vehicle(Invicta), FWD, a midsized FWD car (G6 sized- LeSabre) and the Enclave.
GMC would have the Terrain(in both short and long wheelbase forms, to efficiently axe the Acadia.) The Canyon and Envoy would be mechanical twins, as the Sonoma and Jimmy were, and would be built on a SWB Lambda. Using the 3.0 and 3.6DI as their engines. Then the Sierra and Yukon, which would remain BOF, as they aren't going to disappear overnight. And rather than just a Savanna for contractors, the GMC Savanna is a conversion van only, and its the nicest conversion van this side of a Cadillac.

That leaves the B-P-G lineup with a
Solstice/Astra
Grand Prix/Firebird
Bonneville/GTO

Invicta
LeSabre
Enclave

Canyon/Envoy-Lambda
Terrain (Long and Short Wheelbases)
Sierra/Yukon
Savanna