1) We are now almost three weeks from the last "we'll have an announcement soon" statement from the developers. This is not soon.
2) MS had a place holder slot for Honest Hearts with vendor supplied graphic, which presumably means they where given a date for it and that date got missed.
3) Print publications, with long lead times, appear to have been given a peak at the 3rd DLC, and told they could run the story in upcoming issues, despite the fact that there is still no public announcement.
4) Reference letters for laid off Obsidian folks are seem to indicate that significant portions of all/most later DLCs are done. The combination of layoffs and glowing letters usually suggests that there a money problems. Nothing solve money problems like releasing software.
5) The developers have enough time away from developing new content to fix bugs. While always a good think, its the new content that pays the bills. Obsidian people is keeping its remaining employees busy without getting new software out. Pretty big hint that they have something they expect to bring in new money soon, without additional direct work.
6) The 1st DLC when non-exclusive much earlier than people thought. While we don't know anything about the contract, it is not inconceivable that this was triggered by low sales numbers. IE, MS guaranteed that the Xbox version would sell at least enough to recoup costs, and when it didn't gamesas was free to open it up.
7) Even a casual read of the forums suggests that fans are unhappy with the radio silence and that the delay is costing gamesas money.
8) An official tease would quite people down and help to hold interest. Even if the DLC got bumped a week or two from the initial date, an announcement of some sort is in gamesas's best interest. And it has been since at least March.
Conclusion:
The 2nd DLC is probably done. It has probably been done for a while now. The 3rd DLC is probably mostly done. The 4th might be done. The lack of both a DLC and an announcement of the same is probably the result legal matters forcing both gamesas and Obsidian to hold radio silence. It might be the result of a falling out between the two, or it could be related to the dust up with Interplay. It could be something else entirely. But whatever is holding things up, its not related to creating the DLC. Its almost certain to be a legal matter.