After finally destroying Kid Buu at the end of a long, protracted battle, Goku wished that he would reincarnate as a good person in his next life. That wish was granted, and at the end of Dragon Ball Z Goku met Uub, the human reincarnation of Buu. Realizing that he had naturally become a strong fighter, Goku decided to take Uub and train him up into someone who could step in as Earth's guardian once he was gone.
Uub is potentially one of the strongest characters in the Dragon Ball universe due to being the reincarnation of Buu. Despite this, Uub really does not get a lot of chances to show that potential, often being regulated to a side character role in the few times he does actually get to show up. As the Dragon Ball timeline continues to inch towards the future, it would be great to see more stories that feature Uub and his place in the Dragon Ball world.
Uub's Presence In The Dragon Ball Franchise
As he appears at the end of the original Dragon Ball manga (therefore the end of the original timeline), it's pretty hard for Uub to feature in the main series. Even Dragon Ball Super takes place to early for Uub to actually play a big role, since it occurs before the End of Z. Uub's most frequent appearances occur in the Dragon Ball GT anime, where he gets to play a decent supporting role in the series. Despite that, Uub still doesn't get to play as much of a role compared to characters like Pan or Trunks.
Uub is one of the few characters to avoid being controlled by Baby, and fights with him after fusing with Buu to become Majuub. He is later part of the fight against Super 17 and the Shadow Dragons. However, Majuub never gets to play anything more than a supporting role in these fights, as Goku (and occasionally Vegeta) are always the main heroes in each arc. GT ends with Majuub's contributions being rather meager, despite supposedly being one of the strongest characters in the series at that point.
Opportunities To Explore Uub's Background
As stated before, it's hard for series like Dragon Ball Super to feature stories about Uub because his introduction is still an event that occurs in the future. Uub can't really meet Goku or any of the other characters because they're not supposed to have met until that fateful World Tournament. Having said that, it's not impossible to feature Uub in a story without going past the End of Z.
While Uub has yet to be introduced properly, he has already been born, a fact that has already been referenced by Goku and other characters many times. Because of that, while it's not possible to tell stories about Uub with the rest of the Dragon Ball cast, it is possible to tell a story about his childhood, before he headed off to the tournament where he met Goku. Such a story could do much to develop Uub as a character and give him more background for fans to latch onto. While it's not likely that the story would be all that long, being able to see Uub living in his village with his family could make him a more fully-fleshed character that fans would want to see more of.
Uub As The Future Defender Of Earth
The future of Dragon Ball has kind of become a big question mark, as Dragon Ball GT is largely considered non-canon. As such, there has been more and more interest in seeing what series like Dragon Ball Super have in store. Stories set in Dragon Ball's future would be a great place to set stories about Uub, as he will have already met Goku and even undergone some training with him. There isn't even a need to have Super move past the End of Z; a flash-forward movie that jumps forward several years is more than doable, and it would allow Uub to have a chance to take the spotlight for once.
As someone who Goku has essentially declared his successor, Uub cannot just be another strong character in the Dragon Ball cast list. He needs to prove his ability to succeed Goku by defeating a foe with the same level of strength as Goku's greatest rivals. Seeing Uub work as a Defender of Earth while Goku, Vegeta, and the classic Z-Fighters sit back would really solidify Uub's status as a successor to the iconic heroes, an image that he doesn't really have among the fanbase. Seeing older versions of Pan, Goten, and Trunks working and interacting with Uub would also be great, allowing for the creation of a new generation of Z-Fighters. While it's unlikely that such a story would happen, it would be nice to see Uub featured in a Dragon Ball story in the near future.