Google's Galaxy Nexus is released with Android OS 4.0, featuring the new Face Unlock functionality.
2) July, 2012
Half-implemented solution for multiple profiles is found in the Google code of Android 4.1 (with the feature disabled).
3) September, 2012
Google won a patent on the face-to-unlock functionality, first introduced in Android 4.0.
4) September, 2012
Google also wins a patent on multiple user support using face-to-unlock so each user can access their own homescreen on the same device based on the authenticated faces.
5) September, 2012 (very recently)
According to GSMarena.com, a tipster of theirs said the next Nexus will run 4.1.2 and will have a new "extra lockscreen functionality".