What would the "pay off" of that be for the books? What overarching impact will it have? And will the amount of pages dedicated to her so far in the books be worth it if she's killed off?
Ned's death was huge, he was the defacto main character of the first book, but him dying didn't feel like a cop-out death, it set major events rolling, and you didn't feel cheated for having read so many chapters about him.
In contrast Quentyn was handled poorly, the chapters didn't add anything to the overall story, and his death was "meh". Sure, it'll have consequences for the Martells, but they can't blame Dany for it.
Anyway, my point is, would Cersei dying be more in the vein of Ned or Quentyn. Not sure how he'd manage to make it "mean something".