In lieu of a full-fledged follow-up series detailing the adult adventures of Team Avatar, The Legend of Korra prominently featured most of the iconic team on screen, oftentimes exploring their lives after the defeat of Fire Lord Ozai. However, one notable exception was Sokka -- though he did appear, much of his life is still light on details.
Known to be the chief strategist of Team Avatar, everyone's favorite boomerang expert actually had a wide and varied political career both at home and in the world at large. He also never stopped being the caring and helpful friend and mentor he gradually became in the original series.
It needs to be said that, by the time of Korra's first episode, Sokka has already passed away, meaning he would inherently appear less than his other living friends and sister. Though Aang is also gone, his lasting role as the Avatar, and his surviving children, give him more of a presence than Sokka, who seemingly did not have any of the latter. The show also never provides Sokka with any adult long-term romantic relationships, further limiting the number of characters who could uphold his legacy for the new generation of heroes.
Immediately after the end of the war and Zuko's coronation, Sokka played a role in the Harmony Restoration Movement, aiming to rid the Earth Kingdom of forced Fire Nation settlements. Though he initially chose to help Toph at her newly opened metalbending school, he eventually joined the rest of the team in the Battle for Yu Dao, in which the Earth Kingdom attempted to forcibly remove a Fire Nation colony that had long integrated into Earth Kingdom society and wanted to stay. Along the way, Sokka helped Zuko look for his mother Ursa, helping his friend to recover her stolen identity from the Mother of Faces, and supported Aang in facing off against the ancient spirit Old Iron.
Returning home to the Southern Water Tribe, Sokka faced off against Gilak, a former ally of his father, who was attempting to rid the Southern Water Tribe of the influence from the Northern Water Tribe by making inroads in the South to tap a source of oil. The conflict went so far that Gilak even captured Earth King Kuei to exchange for Sokka's father, who was in favor of working with the North. Led by Sokka, the team managed to defeat Gilak, although his message continued to resonate, leading to the conflict that would become the Water Tribe Civil War.
Meanwhile, his continued involvement in Earth Kingdom politics, stretching back to his participation in the Battle for Yu Dao and its aftermath, led to him playing a pivotal role in the governance of the newly established United Republic of Nations, a fifth nation designed for the unity and harmony of people of all four original nations. He would serve as the representative of the Southern Water Tribe on the nation's council, and as its chairman, he would sentence Yakone to life in prison for bloodbending. This political experience led to his selection as a chieftain of the Southern Water Tribe, a role he presumably held honorably until his death.
Outside of his official duties, Sokka helped to save a young Avatar Korra from a kidnapping attempt by the Red Lotus. He would also leave stories, drawings and advice for Aang and Katara's son Tenzin, perfectly playing the role of the fun but responsible uncle.
Ultimately, much like the rest of his friend on Team Avatar, Sokka's role in his adult years, and his legacy after his passing, was one of actively working for unity and peace between the four nations after the ravages of a century-long war. He not only brought together the two water tribes, a bond which was only broken after his passing, but also the entire world in the form of the United Republic and Republic City.