We already have a gazillion threads on this topics, so I'm just going to copy/paste
what I wrote in another one:
My dream DLC would revolve around restoring Winterhold to its
former glory,
AND I'd also like it to focus mainly on magic and on how this aspect
of the game can be improved. More spells, usefull staffs, spellcrafting, you name it.
I'd also like to see some more activities within the College, especially after you're
named Arch-Mage, like making important decisions for the future of the College such
as if the College should allow services to the rest of Skyrim, and if it should open up
more.
I'm thinking something along the lines, that http://www.uesp.net/wiki/Skyrim:Whistling_Mine (a failing mine on the road
from The Pale to Winterhold) might strike some mysterious mineral that would draw
scholars and merchants alike to the frozen hold - and thus boost the economy of the
place. You would then find out that the material holds extreme arcane potential, and
may have been the true cause of the Great Collapse in the first place - but it also holds
the power to raise the city once again. The material would then be stolen by [insert bad guy]
and you would have to seek allies to help fight them and to take back the mysterious
arcane material.