Google announces firmware upgrade Android 4.0 Ice Cream Sandwich for Samsung GALAXY Nexus S GSM/UMTS model. The update is already rolling in stages and will keep rolling in the next month or so until everyone receives it.
The announcement was made by
@GoogleNexus on Twitter hours ago after the update was tested last week by Google employees with a Nexus S smartphone. We will get back to you with more details about this upgrade (change log), until than check for some highlights about Android 4.0 ICS OS here.
Check for an update on your Android device and if someone manages to pull the update please get back to us and leave a comment down below.
Download Android 4.0.3 for GSM Nexus S (not the 4G version). Installation done manually if you know how to do it please go ahead if not wait for further instructions.
source RootzWiki [for the download link]