I would love to see Bi-Han turn good and atone for his sins as Sub-Zero, especially since it's possible for him to be cleansed and become the Elder God's Champion after he was kicked into the Soulnado, following the events of MK9.
It would bring a great new side to him that hasn't been seen before.
Bi-Han and Scorpion burying the hatchet would also be awesome to see, with 2 rivals uniting to take down a common enemy (Quan Chi).
It would also allow for NRS to move beyond the Scorpion and Sub-Zero "revenge" bullshit story that we've been fed for the past 22 years, and also expand on the characters with a new original story.
Maybe Sub-Zero can even become the new Lin Kuei Grandmaster in MK X, and use that position to aid Raiden and the Forces of Light.