The writing is on the wall. Without any prophecy it’s obvious that Cersei will kill Jamie or Jamie will kill Cercei. (Or they die together at the hand of another).
The most likely being Jamie kills Cersei, as he recognizes the woman he loves is absolutely insane and evil. They may love each other, but her actions killed far mor than just their enemies and cost them their final child as well. My guess would be when the city is about to fall to its enemies Cersei will want to blow the whole thing up with wildfire and Jamie will kill her just as he did the mad King.
Theory: Jamie died at Arya’s hands at the Twins, along with old man Frey. It is Arya in Jamie’s face awaiting to kill Cercei.
“The most likely being Jamie kills Cersei, as he recognizes the woman he loves is absolutely insane and evil.”
Possible. However, keep in mind what Jaime said to Edmure Tully - tied up in the tent outside Riverrun: if necessary, he (Jaime) would kill EVERYONE in order to get back to Cersei.
Of course, he may have just been using a bit of hyperbole to scare Edmure into submitting...