Brody won't die because then his entire family would just become a completely wasted plotline. In Game of Thrones Eddard's family could actually continue to be relevant and drive the narrative. They aren't just going to throw away an entire plotline, arguably the most elaborate one outside of Abu Nezir, even ahead of Carrie's struggles with being bipolar. They aren't killing Brody until the series ends (or one of the last few episodes) if they kill him at all. To think otherwise is naive or think that somehow the writers would be able to keep the show going after completely removing two years of plot/character development involving an entire family that easily represented more than half of the entire show. I shouldn't even have to say it, but its also incredibly obvious that he will be alive at least as long as Nezir because Brody is literally their only useful informant on him and the CIA seems completely incompetent and incapable of doing anything substantial without him (although it could be argued that he also prevents them from doing anything as well I suppose).