Speaking to Vulture, AMC president Joel Stillerman said the show would continue as long as the storytelling in the comics, written by creator Robert Kirkman, stays at the caliber fans have come to expect.
"The answer to how long the show will go on in some way is directly correlated with the health of the storytelling in the comics," said Stillerman. "Those comics are firing on all cylinders. He still writes every line of dialogue in those books, and is as engaged as he was when I think he was sitting around in Kentucky writing the first issue. That is very much part of the DNA of the show. He sort of felt like, in real life, this goes on for a very long time. We’re along for that ride."
Stillerman likens the shows's continuation to Kirkman's philosophy, that the series be about an unending zombie survival tale. "...If you ask Robert what his motivations were for writing 'The Walking Dead,' he would say, 'I loved zombie movies, but I just felt like the worst part of them was always the ending. You always had to manufacture some ending.' So he set out to write this totally open-ended story, and the proof of that is in how vibrant the comics are."
Currently in its sixth season, "The Walking Dead" airs Sunday nights at 9/8c on AMC.