Maybe some underground fighting a la 'fight club' with illegal money and shady people come in a dlc.

agreed

If one exists in Windhelm, then it'll probably be included in DLC. I can live without it - in Oblivion, my 'grand champion' seemed like less of a warrior than someone who stays out of the Arena.

Nice, didn't know those files existed. Now I have high hopes to see it in-game.

Considering that 80% of the stuff is already in the game (albeit unused) I wouldn't consider paying for a such a DLC a fair deal.

People worried that an arena in Skyrim would feel a bit out of place should re-read the description I gave earlier. It's called the pit and probably it looks closer to a proving ground than the glorious arenas portrayed in classical lore.

Actually I wouldn't mind for a DLC with such content. It seemed like the pit was an interesting idea that Bethesda just didn't pursue due to time and money constraints (remember that voice acting is very expensive: not only do you have to voice every NPC in Skyrim, you also have to record them in 5 or more languages and fit those accordingly). Oblivion had a cut questline where you start as a mere courier in the Imperial city and would eventually rise up in the ranks of nobility, with political undertones. That seemed like a very interesting questline to me (certainly more interesting than the main quest). Ah well, different opinions, I guess.