That is one thing I think is cool about GOT. Even main character die. I for one was surprised when Ned Stark died in season 1 and that his wife and son Robb are killed in season 3. Clearly, in this series, anyone is fair game. I am not saying that any one or all will die, just that there is no reason to think they won't.
If they did who would the story be about? Those are the main characters. Danerys might conquer the 7 kingdoms so she can't die yet. Bran is learning to control his powers so he can't die. Sansa and Theon are on some sort of journey. Tyrion has such a great personalty and his story line is intriguing.
No, those characters from Game of Thrones will not die in season 6 because they are popular characters. Usually, the characters in a show that get killed off are the ones that are the least popular or just ancillary characters to the main story. These characters are too central to the things that happen, and because the show is popular, producers will want to keep the show going for a while.
For the sake of the show wanting to create more excitement and enthusiasm the show will hopefully not end the reign of these characters. The possibility of one or two, or the thought put into the minds of the viewers that maybe all will be demised is a possibility! Let the season begin!
While the uncertainty of the fate of the characters of Game of Thrones is one of the main compelling elements of the show, it seems unreasonable, even by Game of Thrones standards, to kill all of the characters that viewers have known since season 1. It is unlikely that all of them will survive, however.
Although Game of Thrones likes to kill off important characters, so many of them won't die in a single season. Without Tyrion, Daenerys, Arya and Bram several plot lines will end suddenly and the story will have trouble moving forward. One or two characters from this list might die, but not all of them.