Howard states this in an interview with Kotaku;
- "With the launch of Mothership Zeta, Bethesda's met Howard's goal. Five game-expanding pieces of content, each granting players about four hour' worth of game time for $10, are now out on the Xbox 360 and PC. The packs are planned for a PlayStation 3 release this next month, with, according to Howard, about one new one per week, starting with the game's end-changing and level-cap-raising Broken Steel."
The first add-on for the PS3, Broken Steel, is expected in September.