This is what the fix is on the legacy platforms (the non greek alphabet platforms).
Anything that's not the Cobalt and the other Delta cars that doesn't have an eared key cylinder will be getting that fix. It's basically a piece of plastic that glues in to your current key and prevents the weight of your keychain to pull the key towards the bottom. At least that's what the theory behind this is.
The N body cars (Malibu, Alero, Grand Am) and the W body cars (Impala, Monte Carlo, Grand Prix, Intrigue) will be getting this fix.
The Cobalt, HHR, G5 and Ion are getting the new key cylinders.
There is no real reason to take a legacy GM car to get the "fix" It's a stupid fix anyways. They will not be fixing your ignition key problems, something that has been known to be bad since VATS (the pellet keys). A bit of a background on that statement - VATS is also known for disabling your car. Sometimes the resistor in the key is bad, sometimes it's the key cylinder itself. It's basically the same issue that the N bodies have with Passlock.
For all of you guys who have sticking key cylinders, loose key cylinders, or the key simply comes out, your fix is on your dime, because GM is not recognizing that their key cylinders are the real culprits. Anyone with the "security" light won't be getting their issue fixed either.
GM will not be replacing the whole ignition key unless someone presses that the issue goes back to the days when they got rid of the eared ignitions. This is why the Buick Regal and Century are not part of the recall. They have eared ignitions. I believe the 1997-2003 Grand Prix isn't a part either.