Also the way Jamie will be redeemed is because all knight with Dragon Steel will need to be called to the wall to defend against the White walkers then when he survives he will be pardoned. The lanisters will turn on the Freys as they turned on the starks. White habour will play an integral part in the dance. Ramsey must die. Bolton must breed his Frey Pig.
Just like "The late Walder Frey" being there is what matters.Everyone who joins the fight after Mance is late. That includes the knights watch. And remember the seasons last years the fight wuth the walkers, that battle may take decades.