So I guess they probably will have to move the timeline forward in the show if it keeps going for years. As long as Carl is around they'll probably need to move things along faster to reflect the actor's age.
The amusing thing about season three right now, to me at least, is that the show's timeline has been moved forward and
the story is still moving somewhat in the same direction as the comics (in terms of location timing at the least). Here's hoping the interludes between each subsequent season won't involve the characters driving around in circles.
The only way to avoid that [or something similar] is to kill off or recast Carl (or, as one site called him, "Anakin"
). Since there is at least a six month gap between when seasons are filmed they need to account for the actor playing him's aging.