Tenzin

Tenzin is the son of Aang and Katara in the upcoming series Avatar: Legend of Korra. He is knowledgeable in Airbending, and the new Avatar Korra is searching to find him and learn from him. Not much is known about Tenzin so far, as Legend of Korra will not come out until 2011.

Rumors & Speculation
These storyline elements remain unconfirmed.
 * His name may be based off of "Tenzin Gyatso", the shortened name given to the Dalai Lama, also part of the name of Aang's master, Gyatso.
 * It is possible that Tenzin could have a personality similar to Gyatso and Aang. However it is unkown what his personality is at this stage.
 * It is also possible that monks are referred to by their last name by other monks of the same level, so Monk Gyatso's first name may have been Tenzin and thus that Tenzin was named after Aang's beloved master.
 * It can be presumed that following Tenzin's birth Aang was no longer the Last Airbender while he was alive. It is currently unclear if Tenzin will be the only living Airbender in Avatar: Legend of Korra, as he is the only one who has been confirmed but the possibility of further Airbenders being alive hasn't been ruled out.
 * During Avatar: The Last Airbender, Aunt Wu tells Katara that her third great grandchild will be born before she passes away in her sleep.
 * If this prediction came true it would mean that Tenzin may already be married and a father, possibly even a grandfather, by the time Korra meets him.
 * Also if this prediction is accurate and Tenzin has a young grandchild at the start of Avatar: The Legend of Korra this would indicate Katara lived a long life.
 * Even if the prediction was accurate Katara and Aang could possibly have had other children through whom their line was continued through, rather then Tenzin, to the point that Katara could have seen the birth of a third great-grandchild before her death. At this time however Tenzin is their only confirmed child.
 * As Katara could still be alive during the new series it is possible that Tenzin might have a child who has got married or is near to marrying age. So the prediction might be fulfilled during or after that series.
 * It must, however, be noted that Aunt Wu's methods are fallible and she has admitted that the future can be shaped by the actions of individuals. Hence whether or not her prediction is in fact relevant and accurate to Aang and Katara's future is unknown.
 * The marrying age in the Avatar World, at least within the Water Tribe, is 16 (presumably for both parties). Thus if it is accepted that the Avatar: Legend of Korra is set 70 years after Avatar: The Last Airbender, with Aang having died sometime between 151 and 154ASC Tenzin's maximum possible age is between 66 and 67.
 * Tenzin being 66 at the oldest seems more likely because Aang was only 12 years old (biologically) at the start of The Last Airbender and only 6 months worth of time is clearly shown to have passed during the series, as both solstices occur within the series.
 * Tenzin's age is however likely to be lower than 66.