At some point, Jack asked MiB or said to Flocke "I dont know what you are" - or somethign to that effect and then Flocke responded "Sure you do".
I think at we are going to find that we've been told the ending already... we just didnt know it. Thats what I am hoping... that we'll be kicking ourselves because in Season X episode Y they said something that was linked to some other episode in a different season that when you put it together we get the answer.
I'm looking forward to the next couple of weeks!