Bethesda has confirmed they're "knee deep in testing" the DLC for Fallout 3 right now, as each need to work with the original game and each other.
Broken Steel, the one that raises the level-cap and removes the ending, will be the first to arrive as it's "easily the most requested" from fans. Then it's Operation: Anchorage and The Pitt.
"So when can you expect Fallout 3 DLC? We are knee deep in testing at the moment, and we’re hoping to have the first DLC out by the end of September," posted Bethesda's Ashley Cheng on the US PlayStation.Blog.
"That long? Keep in mind that not only do we need to test each DLC on PS3, we also need to test each DLC when used in conjunction with each of the other DLC, as well as all of them together, along with the entire original game."
"After Broken Steel, we’ll be releasing Operation: Anchorage and The Pitt shortly thereafter, probably at the same time – just to get them out to you as soon as we can." Just hang in there!