Check out this leaked Game of Thrones concept art which reveals a major plotline for season 7:
More Spoilers Below
According to the leaked Game of Thrones plot, a lot of major characters are expected to be part of this scene.
Meeting at the dragonpit with basically everyone. They demonstrate the reality of the white walkers and it terrifies Cersei (apparently the Mountain[or the Hound] chops up the wight and it keeps moving, Jon shows them the only way to kill it is with dragonglass or fire). She tells them she will send forces to help defeat the undead, but admits to Jamie she was lying. She wants the undead to clear out as many of her enemies as possible. Disgusted, Jamie begins to ride North. Likely happens episode 7. (Cersei, Tyrion, Dany, Jon, Jorah, Varys, Missandei, Qyburn and The Mountain all filmed together at Italica! WotW has confirmed the scene involves bringing a wight into the Dragonpit as proof of the White Walkers.)
If you are interested in reading the entire leaked season 7 plotline, click here.