On July 26th, Jason Bergman replied to a user on the Bethesda Forums, saying that the Fallout: New Vegas DLC Lonesome Road "will be out in August. We delayed OWB because of the patch. We don't have that worry with LR."
We will probably see a more exact date very soon.
Here is a link to the thread: http://forums.bethsoft.com/index.php?/topic/1213217-soo-when-is-lonesome-roads-release-date/page__st__40/