User blog comment:Dak47922/Terraria is coming to Xbox 360 and PS3!/@comment-173.79.5.225-20121228221322/@comment-4674838-20121229011211

Because "they" can't make dlc. And anyways, legal issues aside, one of the top promises of Terraria on Steam was "free updates". DLC would be breaking that promise.
 * ReLogic (company that owns the rights to Terraria and developed the PC version) announced that the PC version was complete (http://www.terrariaonline.com/threads/my-fellow-terrarians.81455/). Nothing will be added to it.
 * The PlayStation and Xbox ports are being published by 505 Games, a different publisher.