While we had hoped to get Dungeon Defenders this year on Xbox Live, PC and PlayStation Network; it looks like we'll have to wait a little longer. According to a post on the official forums by Trendy Entertainment's Jeremy Stieglitz, the four player co-op tower defense RPG is going to be out in January instead. It's not that the game isn't done - in fact, it's complete. The problem seems to stem from the fact it's a multiplatform release and certain "platform owners" are holding things up.
The good news is Trendy isn't resting on their laurels. They've already created two maps and several items that were going to be DLC - but now will be included with the game at launch. If you were planning on picking up the iPhone or Android version of the game - the one that works in co-op with the PC version - you won't have to deal with any delays as the game is coming mid-December.
Source: Forums.trendyent.com