Not watched the leak or seen any spoilers yet, but feeling the need to as cant avoid till Monday.
My guess is Jon Snow and his boys find themselves in a heap of shit. Drogon senses he is in danger and comes to the rescue. Ends up sacrificing himself so Jon can escape, gets downed by the Walkers and eventually turned into an ice dragon.
Regarding Cercei, reckon the baby is either Euron's or there is no baby at all and is using it to keep Jamie close. Either way I can see Jamie killing Cercei in the end.