Kirkman has said specifically in many ego-driven comments that he has no plan to end it. Even the prologue to the entire series says he intends for it to be like "a zombie movie that never ends."
I imagine he will have to end it. Whether he wants to or not. But it does suffer from "sitcom syndrome" as a result, where there's probably no structured story with a beginning and end. Just semi-random shit that happens until they slop together a finale.