Trailers (or gameplay videos, or anything) are usually released like... a year before the release, or close to a year?
Oblivion trailer debuts at E3, May 18, 2005. Slotted for release November 22, 2005 = 6 months prior to release.
FO3 trailer debuts on GameTrailers TV E3 special on July 12, 2008, full version released two days later including gameplay.Game released on October 18, 2008 = 3 months prior to release.
FO:NV trailer debuts on GameTrailers TV E3 special on June 11, 2010, Game released on October 22, 2010 = 4-5 months prior to release
According to Pete the first game play will drop in a month with an "r" in it and unless that is September then it will be in Ma
rch or Ap
ril. = 8-9 months before release.