The lights are on
After the Elder Scrolls V: Skyrim shipped, the team at Bethesda took a week to do whatever they wanted and create content they could add to the game in the future.
As revealed during Todd Howard's keynote speech at DICE, the team designed all kinds of content, including dragon mounts, house building, and spears! Howard prefaced this reveal by saying none of this content is confirmed, and that it may or may not ever come out for public consumption.
The video shown during the keynote can be seen archived on GameSpot. Check it out below. It begins at around the 41:00 minute mark. Here is the list of features that could be added down the road: