Meh can't really see it happening. Halloween is an Irish and Scottish holiday at foremost
and most of Skyrim is Nordic so. A holiday similar to Halloween just dosen't fit tes in my opinion.
Heh, I don't think he means to have the towns decorated with pumpkins and Skyrim kids trick r' treating, but a scary or "zombie" themed DLC that comes out for Halloween.
I loved the hell out of Red Dead Redemption's Undead Nightmare pack, and I see the kind of idea you're going for here with the Draugr but in all honesty I'm not exactly sure how I would feel about it. As strange as that sounds it's just The Elder Scrolls has a very vast backround and I don't see how it would they would be able to implement such a thing.
However, I guess it could be done just like RDR's in the way where it's basically a whole other game that you're loading. That way it wouldn't effect anything in my usual game saves and I wouldn't have random Draugr popping out of graves and junk like that.