I saw the map thing. I'm not saying it won't happen, just that in the TV show there is no suggestion of it happening. If for some reason they decide to to break from the show story line and jump to the book story line, it's just as likely to be Tyrion as Jaime.
The scene wouldn't be as powerful and "bitter sweet"
Picture it, the younger more beautiful Queen crushes KL with her dragons. Cersei is going nuts saying, "kill them all, kill them all". Jaime walks in and she spots him.
Cersei: "Jaime...I knew you'd come back to me"
Jaime: *silent*
Cersei: "I'd **** you right here, brother, if I didn't just have a miscarriage"
Jaime: *silent*
Cersei: "I'm sorry I lost our baby Jaime. We deserved another."
Jaime: *staring and seeming intrigued*
Cersei: "The evil dragon ***** has sacked our city. You must set off the wild fire, my love...but first 1 last kiss"
(Cersei leans in for kiss. The good hand reaches to her neck and caresses her. The golden hand reaches for her throat. The squeeze is applied. Cersei's eyes widen. Tears fall from Jaime's eyes as he squeezes the life out of his sister, his lover, mother of his 3 dead children. Cersei's eyes roll back in her head. A tearful Jaime says, "I love you"...and she dead.
Powerful stuff, huh?