First the comic book, then the TV show, now the video game?
It'll be tough to make a Walking Dead video game that's not simply Left 4 Dead. In fact, the TV series often seemed heavily influenced by the first-person shooter.
For example, it's clear in the comic books that zombies don't climb fences or bash open doors, but some do in the TV series -- just like they do in Left 4 Dead.
They're also a lot faster (when they get "riled up") on the TV show than they are in the comics. Probably two reasons for this -- slow zombies are kind'a boring, and 28 Days Later has everyone expecting fast zombies as well.
(In the original Left 4 Dead, Zoey memorably calls "zombie bullshit" on the speed of zombies in the game.)
Given the fact that all of Left 4 Dead is straight up first-person shooter -- and the fact that most of the Walking Dead comic book series is about humans, not zombies -- I think there's a lot of room for a video game that's more role-playing/strategy than just point and shoot.