Via ATLA Online, we learn the official release date for "The Search - Part 1", and that is March 20, 2013.
The news comes from crunchyroll, and along with the release date we've also gotten a short summary:
"For years, fans of Avatar: The Last Airbender and The Legend of Korra have burned with one question -- what happened to Fire Lord Zuko's mother? Finding a clue at last, Zuko enlists the aid of Team Avatar -- and the most unlikely ally of all -- to help uncover the biggest secret of his life."
So there you have it, folks. In just about five months, we'll start to see the story of what happened to Zuko's mom! No pre-order info yet, but we'll let you know as soon as it becomes available.
UPDATE (25/oct/2012) - "The Search, Part 1" can now be pre-ordered: via Dark Horse; on Amazon.
Going to awesome...