Given that Old World Blues had quite a delay, there have been fears that Lonesome Road, the final Fallout: New Vegas add-on, would be delayed even further. However, Bethesda's Jason Bergman has confirmed that the DLC will be released this month:
It will be out in August. We delayed OWB because of the patch. We don't have that worry with LR.Actual date will be announced soon (don't ask me when, I don't make those decisions).
Still nothing definitive, but we at least know that we won't have to wait until September to finally meet the mysterious Ulysses.