Someone managed to do a little digging to see what was hidden in the Skyrim disc and apparently some areas that were in Morrrowind and Cyrodiiil were discovered locked away.
It wasn't just a quick template or placeholder but ended up being a complete low-res version of Morrowind’s Solstheim and Vvardfell areas along with the Imperial City in Cyrodiil.
A few websites are thinking either these areas will become future DLC quests or expansion-like packs.
http://www.egmnow.com/articles/news/...ind-templates/