In a recent blog post Keith Baker confirmed a new Eberron adventure will see printing early next year alongside the Eberron 4E Campaign Guide and the Player's Guide.
He also included some clarifications on the ECG vs. the EPG vs. the 3.5 ECS:
Looking to the 4E Campaign Guide and the Player's Guide, I want to say that these are NOT simply 4E translations of the ECS and the PGtE. You're not going to see a lot of duplication of material between the two; because they are coming out around the same time, if there's material that is equally relevant to both PCs and DMs, it's going to go in the Player's Guide. So looking to the current ECS, things like feats, dragonmarks, racial descriptions, the artificer, spells, and so on would all go in the Player's Guide. Nation descriptions will be aimed at what you need to know to create a character from a particular region - as opposed to the Campaign Guide, which will tell you things like which noble may be undead, who wants to go back to war and who wants to stop it, and so on. First, this means that there will be a much clearer delineation of "These are things known to the public, and these aren't". Second, it means that we will have room in the Campaign Guide to present information NOT available in the 3.5 ECS... whether it's just a greater level of depth on old ideas or organizations (what's House Tarkanan up to? How do you actually use the Dreaming Dark?) or presenting a few entirely new ideas to play with. With the benefit of hindsight, there are certainly things I wish we'd done differently in the 3.5 ECS, along with issues where we've had conflicts and contradictions between sourcebooks in the following years. MY goal is to have the 4E core books provide a solid and consistent foundation for the setting, and to ensure that they are interesting and useful both to newcomers to Eberron and to people who have been playing it since the start. Of course, I'm not the only person working on the books, and a lot can happen over the course of a year - so I can't promise specific coverage on any specific topics or go into great detail about anything. However, I'm excited by the potential I see in these books, and I believe that we've got far more to offer than just a mechanical update to 4E.