Google has released the open source code for the Android 4.0.4 Ice Cream Sandwich for the Android Open Source Project. The official Android Google+ account stated that the Android 4.0.4 Ice Cream Sandwich update is being rolled out for the Samsung Nexus S, Xoom WiFi and HSPA+ Galaxy Nexus devices. At this moment, the Android 4.0.5 Ice Cream Sandwich update is said to be tested out for the aforementioned devices.
The new Android 4.0.4 Ice Cream Sandwich update is quite generic in nature and is usable for the GSM versions of UMTS/GSM Nexus S, HSPA+ Galaxy Nexus and Xoom WiFi. It is difficult to list out the exact models on which this update works but being generic in nature, it should ideally work on stock ROM running devices. By stock ROM we mean, the device does not have any custom ROM or system level modifications.
Jean-Baptiste Queru, software engineer with Android Open Source Project at Google, noted at the Google Groups that the Android 4.0.4 ICS represents an incremental update of a few hundred changes over 4.0.3 ICS.
As of now there is no official change-log about the improvements coming along with the Android 4.0.4 ICS update.
Back in mid-December, Google had released Android 4.0.3 Ice Cream Sandwich for the Nexus S devices. But after users starting complaining about the faster battery drain issues, Google froze the update roll out and promised to look into the issues.
After a long gap of three months, Google has finally started rolling out the new Android 4.0.4 ICS update. For the Nexus S GT-I9023 and Xoom WiFi owners in India, the update is expected to show up over-the-air and for that patience is expected.