Google has just published the latest Android 4.0.4 (IMM76D) factory image "yakju" for Galaxy Nexus "maguro" (GSM/HSPA+). I've decided to flash the factory image right away instead of waiting for the OTA update.
I've just followed the same instructions that worked to install the Android 4.0.2 ICS.
Be aware that all your personal data (files, photos, mp3, ...) will be erased during the process as a factory reset will be done. You should make a backup before starting the install. You should also ensure that your account's information are backed up on Google's server and that the synchronization has been done.