Soon after the Ice Cream Sandwich announcement, Google stated that it is working on Nexus S Android 4.0 update right now and it will soon be released. Company also stated that Android 4.0 should theoretically work on any Gingerbread device.
In exact words of Matias Duarte – “Currently in the process for releasing Ice Cream Sandwich for Nexus S. Theoretically should work for any 2.3 device.”
There is no word on the exact timing of the update for Nexus S, but it will be released. Company however did not state on the update plans for Nexus One, the first Nexus device from Google.