I just read on the Black Isle Studios forum where this guy posts "I know who the end boss is!", and then when you enter the post, you see that one of the Moderators has erased his answer, so that you cannot see...hmmmso if this guy found out, maybe we also have the ability to surf the net and find out, because obviously, he was right.
Personally, I don't think it is the Demogorgon. They showed that in the live video...they would not show us the end char. on the demo...
------------------
Larry, a loyal guardian of the OHF, and devoted member of the Ironworks