I just finished watching the blu-ray of season 4 and have of course been reading the rumours and such. As I mentioned in a previous post the stuff that Benioff and Weiss are leaving out is a huge clue itself since that can be taken to mean that those plot lines don’t really matter to the culmination of the story (which we assume is the same as planned for the books). Not every character who dies before the end has to die at the same time and place or way but (presumably) every character who survives to play some role in the ending of the story has to live and get there somehow.
Then we have characters who don’t appear to be crucially important but whose story lines have been kept alive in the TV series indicating that they must be after all (although maybe one such story line is a red herring several would be too much).
Sansa Stark
Theon Greyjoy
Brienne
Jorah Mormont
Characters who might die in season five
Brienne of Tarth
Samwell Tarly
Littlefinger
Jorah Mormont