The writer and executive producer told Entertainment Weekly that Merle (Michael Rooker) and Morgan (Lennie James) will eventually reappear.
"We're all suffering from Michael Rooker withdrawal," he joked. "We love him. We want him back."
He added: "It could happen in episode three, could happen in episode seven [or it] could happen in a possible third season. But we're going to get him back."
Kirkman suggested that both Rooker and James "brought a lot of credit to the first season" of the hit zombie drama.
"We're absolutely dying to work those guys back into the show," he admitted. "It's not something we're going to forget. We're not going to abandon these characters."
Michael Rooker previously hinted that Merle could return to The Walking Dead in the near future.
The Walking Dead continues this Sunday at 9/8c on AMC in the US, and airs on Fridays at 10pm on FX in the UK.
> The Walking Dead: 'Bloodletting' recap
Watch the Walking Dead cast discuss season two below: