But your point is fair. At this point, to really change the show, character entrances and exits aren't enough: the "world" would need to change. Things that have been discussed before: a zombie cure, or the real promise of one. A mechanized means of zombie eradication. A settlement of thousands of people, not just dozens at the most, with a means of preventing outbreaks and protected by more than sheet metal walls. Learning that part of America/the world didn't fall. Post-zombie reconstruction and reconciliation would be a fascinating show, for instance. But I think the real-world limits of the show (shooting in Georgia, budgetary constraints), probably mean something like that won't happen. At least not on television.