Jaime and Cersei's split leaves a lot of open questions for the Lannisters.
Jaime Lannister finally found his breaking point: zombies. More likely, it was zombies combined with Cersei’s insistence that he couldn’t be trusted. She calls her lover-brother a traitor -- that hurts. Just when it looked like a baby would soften her up, Cersei inches closer to becoming the Mad Queen. We don’t get to see her lie to Tyrion about marching the Lannister forces North after he guesses that she’s pregnant, but we know it's a lie, because Euron Greyjoy has already secretly gone off to get the mercenary Gold Cloaks in Essos. Cersei kept this decision from Jaime and it pisses him off.
It’s a good scene, but Jaime’s logic for leaving and going North doesn’t sound as much like reclaiming his honor or finally rejecting his sister as it sounds like being frightened by zombies. Jaime isn’t very worried about his word, at least he hasn’t been before when it comes to living-on-living warfare (he is the Kingslayer, remember!), and his sister has lashed out and made dumb decisions before; it seems unlikely that he’d leave his sister-lover because she scorned him. No, Jaime is scared of zombies, which is understandable given how shaken he was about dragons. It just isn’t the final schism between sibling-lovers that it we all expected. If Jaime survives the Great War to Come, he still has family in King's Landing. Maybe Jaime’s ultimate purpose is to stop Cersei, but if that’s so (valonqar ho!), he’s heading in the wrong direction on the map.
Cersei looks locked into the plan to let the "monsters" fight the monsters up North, then pick off whomever comes out the victors. It doesn’t stand up against the reason that if the Northern forces are defeated, they’ll be added to the Army of the Dead, but Cersei is fairly confident in dragons. The Mad Queen Cersei will not be stopped now that she has a life in her, and it sounds like once Euron returns with the Gold Cloaks, she’ll be quick to re-take Highgarden and Casterly Rock while the Unsullied and Dothraki are away. We’ve been told the Gold Cloaks are bringing elephants, which hopefully isn’t just a rumor and is actual foreshadowing for Battle Elephants versus Zombie Giants, which is not the latest SyFy original movie.