But what's the point of Bran controlling a dragon - who seem to do as Daenerys wants - unless it's the undead dragon?
That'd be more useful in a Jon Snow versus Daenerys battle, ah ha so you thought you had dragons as Bran makes one or more fight for Jon Snow, but that seems unlikely.
On another topic, I was thinking about the title of the book series, 'a song of fire and snow', and how while Daenerys is clearly represented by fire, how the connection of Jon Snow by 'ice' was more iffy, and why they had to make it all about Starks in the cold north, and 'winter is coming', and his service at the wall in the snow. But it seems pretty forced. He doesn't have 'cold magic' and such.
Then I noticed his name relative to the 'ice' defining (at least they didn't make Daenerys' last name "Flame"). Seems a bit heavy-handed.