Here is his response, he had actually got a similar email earlier and just gave me the same response.
“I pulled the updated year from Dark Horse’s official note about the comic**. It isn’t terribly uncommon for the local premiere of a television animation to get one or two delays in schedule its premiere date, but I understand the frustration that might accompany the emotions in support of a program as highly anticipated as the follow-up to AVATAR: THE LAST AIRBENDER. To my knowledge, the series had already been pushed back from spring 2012 to autumn 2012, then not unsurprisingly.
I haven’t yet bothered to check with Dark Horse’s publicity department to confirm if the number (2013) is a deliberate update or not, but with so many months until the property emerges in any commercial form, any date should be treated as tentative at best.
I am not even going to bother emailing Dark Horse as I know they won’t reply, I emailed them about the Lost Adventures release date a while back and got nothing (I tried 3 times).
I am pretty sure the date is still mid-Fall 2012