That's because he is doing all of 8.....right......right?
:'(
It would make a lot of sense to bring him back for a bunch of back to back episodes in season 8, to direct the War against the Night King.
Imo Season 7 is going to be a lot of exposition/ dialogues to setup season 8, simply because at this point it's pretty much Cersei vs Rest of the World.
Oh yeah, Euron building ships might offer an alliance with her, but that won't matter a thing when Dany is coming North with more than 10.000 Dothraki soldiers, 2.000 unsullied, 3 Dragons and support from both Dorne and the Tyrell House.
In the North, you have Jon and Sansa which just unified the North, all the way down to the Riverlands thanks to Arya, and "should" soon be joined by the Brotherhood, The Hound and Brienne/ Pod.
LF will be a concern for a while I guess, but given the Northern -and- southern threats all his ambitions came crashing down, lady Mormont placing the final blow by calling Jon the king in the North instead of making Sansa the Warden.
His last play will either be to strike back at Jon (poison/ fire) and/ or go back to KL to try and gain Cersei's favors which logically (other than still trying to woo Sansa, which I don't see happening) is his last shot at the Throne (those two definitely deserve each other).
What would be funny would be LF botching his attempted assassination in WF, fleeing to KL to offer his help to Cersei, Making grandiose plans on how to get her confidence, eventually marrying her and betraying her, only to arrive seeing hundreds of ships in the Harbor, Cersei dead by Jaime's hand when she was about to blow up the whole city (Qyburn fleeing the place with his personal Zombie).
Can't wait to see (hopefully) the scene between LF in a KL jail, and Tyrion with Varys visiting him.