I mean I can't remember a character being so obviously set up to die on this show.

The best Martin can hope for to buy time is that after 7 or 8 seasons they decide to do movies. Otherwise if the show sticks to Benioff and Weiss' plan, we are talking what 3-4 years tops, maaaybe 5 if they try to do some kind of Mad Men/Sopranos break the 8th season in half nonsense.