In the 'Sasuke travels to the future fanfiction', Sasuke might meet some sort of future council that governs the ninja world. They could be a mix of old ninja families and new leaders who emerged over time. Also, there's a chance he meets some sort of future - tech ninja who uses abilities that Sasuke has never seen before, which could lead to some interesting battles or exchanges of knowledge.
He might meet the future versions of Naruto and Sakura. Their relationship with him could be very different in the future, perhaps they are now leaders of the village and Sasuke has to adjust to their new status.
He could meet his future self. It would be an interesting encounter as he could learn from his future experiences and wisdom. Or he might meet people who have studied his past adventures and see himself through their eyes.
Sasuke traveling to the future in the fanfiction would be full of possibilities. He could find that the traditional ninja clans have evolved into something completely different. For example, the Uchiha clan may have developed new and unique powers that are a combination of their Sharingan heritage and future technology. He may also meet versions of himself from different timelines, which would create a very complex and mind - boggling situation as he tries to figure out his place in this new future.
He could meet his future children, if he has any. They would likely be powerful wizards or witches with their own adventures. Also, he might run into the future versions of Hermione and Ron. They would probably be in important positions in the wizarding world, like Hermione might be a headmistress at Hogwarts or something.
She might meet her future children or grandchildren. It would be an interesting encounter as she gets to see the family she may have in the future.
Darth Vader could encounter advanced droids that have developed personalities and even some form of Force - like abilities in this future. These droids might be a new challenge for him as they are not like the droids he is used to dealing with in his own time. He may also meet future versions of his former allies or enemies, who have been reincarnated or cloned in some strange new way, with different personalities but still with a connection to their past selves.
The main characters are obviously Sakura and Sasuke. Sakura, with her strong will and medical ninjutsu skills, and Sasuke, known for his powerful Sharingan and his quest for power and revenge in the original Naruto story.
Sasuke might be initially surprised. He is used to the Sakura from his past, so seeing a different, more mature future Sakura could catch him off guard.
Goten could meet the younger versions of his friends like Krillin or Yamcha. They might be a bit skeptical of him at first. He could also run into Master Roshi, who would probably be interested in Goten's abilities and might try to teach him some old - school techniques. And there's a chance he meets Bulma, who could be intrigued by his futuristic knowledge and might even try to get some tech ideas from him.
Naruto would meet his younger self. This would be a really strange situation. He could also meet all the important shinobi from the past. For example, the First and Second Hokage. He might have a chance to learn from them directly, instead of just hearing about them in stories. Additionally, he could meet some of the characters who were only mentioned in passing in the original story but had a big influence in the past.
He could meet his future self. This encounter might be full of surprises as his future self could have different views and experiences. His future self might be more jaded or more powerful.