And as Random and me have been talking about on PMs, revealing Bran to be the Night King could make for a more satisfying and dark ending. I could reveal him to have warged into Daenerys, or the dragon, right before the slaughter. It would still justify her plotline - slowly losing her mind; because she would still at this point be conflicted and mad and having burned Varys and threatened Tyrion, but instead of the insanely sudden shift to genocide; it would be Bran/NK who would put the final nail in the coffin.
I, personally, think that the most emotional and dark ending would be if Bran was revealed to have warged into Drogon (and not Daenerys) and performed the slaughter, and Daenerys would kind of just have had to stand for what had happened - making the episode 6 material be more of her having been forced to go Mad Queen rather than chosen to do so. It would also make more sense, as the dragons are many times told to be uncontrollable and dangerous throughout the series. Therefore, Daenerys would try to hold face and pretend to be all just and true about what has happened, when in reality she’s completely destroyed. Her death would also be more tragic, because the audience would be the only ones to know that what happened wasn’t really her (dragon’s) doing.
Either way, long time until film 8 (or perhaps 9/10) now - but tell me what you think!
As I said, this is your vision, so you get to choose how the story goes.
What I have read sounds interesting and I am curious to see how it will end up to the final cut.
But for now, I will be waiting for any update about Film III and IV.