Offline Google Maps in the next iteration of Android
This is actually in the next iteration of maps...or rather the last iteration as it was released yesterday. If you upgrade Maps on an Android device, you get this functionality.
The mapping application is simply an app, having been decoupled from the OS back in, I think, 2.3? The labs functionality for offline access has been around for a while, but has been baked into the core app now.
The point being that it isn't an 2.3, 3.0, 4.0, or 4.1 feature. It's a Google Maps feature.
This is actually in the next iteration of maps...or rather the last iteration as it was released yesterday. If you upgrade Maps on an Android device, you get this functionality.