User blog comment:Saratje/PC release date explained - Skyrim: Dragonborn DLC/@comment-5469467-20121123211511

That explains a lot, actually. It seemed a bit odd how little content Hearthfire had, so your theory makes a bit of sense. I'm looking forward to the end of Microsoft's deal with Bethesda, so we can all enjoy the DLC at the same time (PS3 included, hopefully).