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AMC will produce a "Walking Dead" spin-off in 2015. The fourth season starts in less than a month (Oct 13th) and is one of the MOST watched shows on cable TV.
As far as the new series plot, storyline, or characters… AMC isn't saying more than "a spin-off" is coming. There is no working title, only that the writers and producers are on-board for a series that isn't connected to the show or the comic book.