After the main story and the civil war questline, the Thalmor attack Skyrim and the people of Skyrim take the fight to the Summerset Isle. This would be a nice DLC. Since it would be after the main story, what would the purpose of the Thalmor be, storywise? Would everything would go back to normal?

• http://www.gamesas.com/topic/1387719-i-would-like-to-see-a-second-great-war-dlc/page__p__21066459#top
  
• http://www.gamesas.com/index.php?app=forums&module=post§ion=post&do=reply_post&f=178&t=1387719&qpid=21066459
  
• http://www.gamesas.com/index.php?app=forums&module=post§ion=post&do=reply_post&f=178&t=1387719&qpid=21066459

The formatting in your post is all kinds of F-ed up just FYI. Anyways, this or something like this sounds more like something that would be TES 6 rather than a mere DLC. An idea like that is enough to hang an entire game on rather than a short little DLC main quest line.