Sozin's Comet, Part 1: The Phoenix King

This the 1st part of the upcoming 4-part finale of Avatar. These last four episodes will be combined together to create a 2-hour long movie. The kids return to the Fire Nation and prepare for their final confrontation with Firelord Ozai, but they discover that the Firelord has plans of his own: he has ordained himself Phoenix Lord and appointed Princess Azula as the next Firelord. In the spectacular 4-part finale of Avatar Book 3: Fire, Aang fulfills his destiny as Avatar and confronts the Firelord in the greatest battle of the series.

Fan Theories Derived from NYCC Trailer

 * Katara will Bloodbend again.
 * Katara will fight in the Fire Nation Royal Palace.
 * Azula will be confronted by either her mother Ursa, or an image of her.
 * The Comet might come before Ozai is defeated.
 * June the Bounty Hunter will return.

Fan Theories based on Countdown to the Comet Commercial

 * In "Countdown to the Comet" commercial on Nick, King Bumi is seen saying "well, look who's here!" to Katara, Zuko, Sokka, Toph, and Suki. This means that he might find "the right time to strike" and take back Omashu.
 * In the "Countdown to the Comet" commercial, there is a wave of blue flames heading towards Katara, indicating that she may battle Azula.

Fan Theories based on Series Continuity

 * Either Aang and Ozai might both tap into the power of Sozin's Comet or Aang might use the Avatar State and Ozai might use the Comet.
 * Iroh might return and more information on the Order of the White Lotus might be revealed.
 * Zuko may create lightning.
 * Jeong Jeong may return.
 * Sokka's messenger hawk, Hawky, may finally return.
 * Toph's parents may finally accept Toph.
 * Koh may return.
 * Ty Lee and Mai will most likely return.
 * Zuko and Katara might rescue the Invasion Force, The Kyoshi Warriors and maybe even Mai and Ty Lee from the prison Iroh previously stayed at.
 * Ursa may have a touching reunion with Zuko.
 * Iroh, Piandao, King Bumi, Jeong Jeong, and Pakku might be part of the Order of the White Lotus.
 * Ty Lee and Mai may escape and confront Azula.
 * Zuko may rescue Mai and Ty Lee.
 * Aang may master firebending and use Sozin's Comet to his advantage.
 * The Order of the White Lotus may try to retake an Earth Kingdom city most likely Ba Sing Se.