TWD is on its last leg, rating for the last couple seasons have been pretty anemic.
I posted a bunch of articles in the TWD thread to disprove this, I'm just to lazy to look it up. It boils down to this.
TV ratings are down, across the board, broadcast networks (the big 4), basic cable, sports, news, drama, reality, everything. The NFL ratings are down from previous seasons, but down much less than the rest of TV. Same with TWD, ratings are down but
it is still the #1 show on television, because the ratings for everything else are down more.
TV executives don't cancel the #1 show, if it drops to #50 and becomes too expensive, then, yes. Right now the show is a license to print money even though it has become trendy to hate it, people are still watching, then bitching, but still watching.