The young survivor (played by Madison Lintz) vanished in the zombie drama's second season premiere.
"We've followed this story line to the point where everyone in the audience has had ample time to look at all angles to this," Kirkman told The Hollywood Reporter.
"At some point, you were probably agreeing with Rick [that the group should keep searching for Sophia] and now you've gotten to the point where you're kind of agreeing with Shane [that they should give up]."
However, the writer claimed that the mystery of Sophia's disappearance will be resolved in the near future.
"It's definitely not something [the characters are] going to be giving up on," he insisted. "There will be a resolution to that storyline coming up at some point."
Kirkman recently revealed that planning has already begun for a third season of The Walking Dead.
The series airs on Fridays at 10pm on FX in the UK, and continues on Sundays at 9/8c on AMC in the US.
> The Walking Dead: 'Secrets' recap
Watch a promo for the next Walking Dead below: