Thirty hour Oblivion expansion coming in spring

Bethesda plans to release an Oblivion expansion pack called The Shivering Isles this spring, according to GameSpot. The expansion will include more than 30 hours of gameplay in the form of new territories to explore, enemies to conquer, and quests to complete. An entirely new region, called The Isles, will be added to the game. The Isles will be accessible from Cyrodiil using a door that appears in the Niben Bay.

In November, Bethesda released a addon questline called The Knights of the Nine as retail package for PC's and Xbox Live Marketplace download. Although nothing has been confirmed, I don't see anything to stop The Shivering Isles from becoming an Marketplace download as well.

[Oblivion expansion revealed @ GameSpot]