Take this with a grain of salt:
An insider source said the following major characters have been either cut or merged:
1)Arianne (merged with sand snakes)
2)Wyman (merged with umbers, no north remembers, no frey pies, no "perhaps tis was a blessing speech") Umbers will instead oppose bolton because they killed greatjon, not of loyalty to the starks.
3)Euron, victarion and Aeron merged into Euron
4)Stannis will not heed jon's advice and will attack the dreadfort, his forces will be slaughtered and the remaining will take shelter near winterfell "crofters village")
5) No barbara dustin, Alys karstark or Bowen, Jon will be betrayed by thorne.
As I said take this with a grain of salt although the same source told alot of accurate predictions for season 3 and 4 and it turned out true so far.
I saw this on the westeros forum if 12,3,or 4 are true I might just stop watching