Well, that was kinda random. :P Seriously, I can't think of any place where the Bible definitely says one way or the other. That said, the design of Man and Woman, including stuff like the fundamental attributes/tendencies and their typical role in life (i.e., if a child trips and falls, they typically run to Mom, not Dad, since she's the nurturer and caretaker, whereas the father is a protector and provider, stuff like that) is so integral to the Bible and God's creation that I can't imagine that gender would be totally absent in Heaven.