I think Jaime will die. Cersei needs to lose everyone she has ever loved. At some point I believe only Tyrion, the brother she despises, will be the only other remaining Lannister.
Who will Arya disguise herself as? There's a reason she commented on her father's statue in the crypts. "It doesn't look like him." or something to that effect.
I'm betting this is Jaime's last season, but Cersei won't know he's actually dead and Arya will disguise herself as him for one last romp...
He'll make it out of the water though.