i like the idea of headless horseman DLC, especially because when you follow him he takes you to a graveyard which i assume to be where he was buried, and does NOTHING
The headless Horseman Dlc is very probaly.By three reason:
1-You can interact to him,But not talk to him.i think that his dialogues are hidden because, on the Skyrim:Demo from Quakecon,you could talk to the giants and also had the same option.Homever,the option was removed,but you can see the same option "of talk" on the Horseman.
2-His horse can be obtained via Console Commands.
3-The same thing happend before Bioware realeased "The Shadow Broker DLC'.There was a option of dialogue with Liara.Homever you couldn't acivacte this option.