from the sound of it, we'll probably see the source code around the same time it gets released for the nexus S. This should happen by the middle of december.
http://thisismynext.com/2011/10/19/ice-cream-sandwich-update-roadmap-andy-rubin/ this is where I read it from. I guess saying by mid-december makes it sound alot more far off then it probably is. It was an assumption on my part that the next phone to get it would be a nexus s. All this being said, we should be seeing the release of ICS's source code sometime in the nov/dec timeframe.