They could have extended Brans story into season 5 by including his journey north of the wall with Cold Hands and Sam. Another plot that I was really hoping to see.
This hits on one of the most disappointing things about the show. With all the pre-written material, and the known endgame, they had every opportunity for seamless characterization and growth over the course of the show, but have scripted via the same season-to-season pitfall of traditional television. They script out one season at a time. Thus Bran disappearing for a season, Sansa going from pawn to player and back to pawn amd back to player literally every season, the Dothraki dissapearing for multiple seasons, the Dorne plot being so screwed that they just killed off the characters they'd written into a corner, Gendry, no LSH, no (f)Aegon, no prophecy paying off seasons later. People will blame the medium, but really the showrunners have done a terrible job of planning future seasons.