But those kind of curveballs are what really made this show great, right?
The story of a boy who was out for vengeance against a corrupt king that wrongly executed his father. A boy who became king of the North, who built his forces and marched south for one last great batt.....Oh wait nevermind, he dead.
Some of the big plot points have become kind of predictable lately. Everyone knew Jon Snow was going to get resurrected. Everyone knew the Knights of the Vale were going to ride in at the last minute to save the day at BotB. It would have been a neat little twist and in the show's character to guide Jamie towards redemption and the overwhelming prediction that he's going to kill Cersei, only to cut it short.
But yes, I agree, in the current show there is little chance Jamie is dead. He will likely escape from the water off screen and continue down his path of redemption which ends with him killing Mad Queen Cersei, which will come as a complete shock to all the Noonan's out there that watch the show while playing Words With Friends.