http://www.avatarspirit.net/

According to Nick, there will be 21 chapters of Book 3 of Avatar, and one of those chapters will be a hour long (Day of Black Sun.) Which means, technically, that there will be two extra episodes this season.

The series finale is going to consist of four episodes/two hours, so this means of course, that none of us will be alive by the end. GET THE GRAVES READY GUYS.