The Halo Council
According to IGN the Halo 4 embargo will be up at 12am on November 1st, so expect the flood games of content, gameplay, reviews etc to be hitting around that time. It's almost fitting since November 2nd is the start of MLG Dallas.
http://halocouncil.com/content.php?r=954-Halo-4-Embargo-Up-On-November-1st!