I think General Motors is faking the demise of the "Chevy" name.
General Motors is emblematic of bailout angst. They're not going to be more hated by dropping a loved brand name. They're already at the bottom. However, by threatening to kill Chevy, they can make Chevy fans rally around the Chevy brand. They'll take Chevy's side to protect it from being crushed by big, bad GM.
GM loses nothing. Chevy gains support. Chevy sells more cars. Chevy is GM. GM sells more cars.
(See also: New Coke?)
That's my opinion. On the other hand, maybe they're not faking it. Maybe they're serious. Or maybe, if they know GM isn't going to turn the corner anyway, why not just step on the gas, blow through the guard rail, and crash fantastically over the edge of the cliff in a meteoric blaze?
(From a collector's item Pontiac owner.)