From the new Awakening interview (see the news):
IGN: Origins has been supported by a large amount of DLC from launch. The most recent of which, Return to Ostagar, has been delayed until the end of January at the earliest. Is there any explanation as to why the delay occurred? Is it solely to release the DLC for all three platforms at the same time, or was there another issue?
Fernando Melo:No, it has nothing to do with platforms themselves. It's a quality issue where, literally, at the last minute, we spotted something that had made it through our own testing, EA's testing and was at Microsoft already. But it applies to all three platforms; it wasn't something specific to Microsoft, we just happened to catch it there first. We probably could have gone with it, but it's something that was serious enough that we felt it impacted the quality [of the DLC] and we made the choice to delay it to give our fans the best experience with it. That was the reason behind [the delay] -- we want to make sure that we don't cut any corners when we do the DLC. There's already a lot of content out, there's a lot more coming -- we just announced the expansion pack, and there's more coming after that. I think the worst thing we could do after that is do anything "to poison the well," to use the expression, or put fans off from feeling that they're getting the best content from us. It's a long term decision instead of a short term decision.