User blog comment:Saratje/PC release date explained - Skyrim: Dragonborn DLC/@comment-99.111.76.129-20130105181410/@comment-74.96.245.203-20130107082351

It could be because of the steam xmas sale that included skyrim, maybe they wanted to let that finish oh and the PSN updates on Tuesdays so maybe they'll wait till then to release it. Or not I dunno but that's my best hypothesis.