In a Frikidoctor YouTube video of 7 months ago they told the public a couple of things:
Tyrion Lannister will be the one responsible for a fire that will kill thousands of King Landing’s inhabitants
He will walking through the streets of King’s Landing accompanied by Jon and Bravos
The actress of Yara was also there on set
There will be a trial held for Tyrion at the Dragonpit, where he will be executed for treason.
There is a possibility that Jaime will die, might be in the hands of Brienne
Melisandre will fight the Nightking with the dead she controlled
There will be two new characters introduced (they were on the set filming)
Well those are the leaks Frikidoctor provided us.
Thanks to NippleFlicks from reddit for providing a good list.