As of now, Naruto and Sasuke haven't died in the Boruto manga. Their characters continue to play significant roles and contribute to the story's development.
Sasuke often appears in different story arcs of the Boruto manga, depending on the current plot and mission. Sometimes he's on a solo mission, sometimes he's involved in events related to the village.
Boruto's character development could be a complex journey. At first, he may feel overshadowed by his parents' fame and power. This could lead to him acting out or trying to prove himself in the wrong ways. However, as he experiences more of the ninja world and faces challenges, he starts to understand the true meaning of his parents' actions. He might develop a more empathetic side, seeing things from the perspective of others, especially those affected by Naruto and Sasuke's past actions. He also grows in terms of his combat skills, learning from both his father's brute force and Sasuke's finesse. His character arc could be about finding his own identity within the context of his parents' great reputations.
Naruto is likely to be popular too. Even though it's a Boruto x Sasuke fanfic, Naruto's relationship with both of them is so important. He could play a role in supporting them from the sidelines or even getting involved in a crucial part of the story.