Naruto is the central character, no doubt. Hinata could be important as well. If Naruto sees a future related to his family or his relationship with Hinata, she will play a significant role. Additionally, the Hokage, like Tsunade or whoever is in charge at that time, would be important as Naruto may need to report the future he saw to the village leadership to take collective action.
Well, perhaps Naruto sees the future where his friends are in great danger. So he tries to change the course of events. He might start to make different decisions in his present to avoid the bad future he has witnessed. For example, he could try to resolve conflicts with certain characters earlier to prevent future wars.
Well, it could be that James Potter sees the future and tries to prevent a great tragedy from befalling the wizarding world. Maybe he sees Voldemort rising to power earlier than expected and he has to figure out a way to stop it without changing too much of the future.
Well, one possibility could be that Naruto has some sort of visionary ability where he can see snippets of the future during his past adventures. For example, he might see the final battle against Kaguya while he's still on a mission with his team as a genin. This could change his approach to training and how he interacts with his friends, as he tries to prepare them for what's to come.
It could be about Baby Sakura having visions of different possible futures. Maybe she sees a future where she becomes a great hero and saves her world from a terrible danger. Or perhaps she sees a future with new friends and exciting adventures.
It could be a future version of himself that has become corrupted by power. He sees this future self causing chaos and destruction, and has to find a way to stop his own dark path. Maybe it's a result of his technology getting out of control and warping his mind.
One possible plotline could be that Tony Stark sees a future where his technology is misused and he has to find a way to prevent it. For example, he might see his Iron Man suits being used for evil purposes by a powerful villain. Another could be that he sees a future without him, and realizes the importance of training a successor, like Peter Parker, more seriously. Or he could see a future where the Avengers are disbanded due to internal conflicts, and he tries to mend the relationships in the present to avoid that future.
Lily Potter would also be involved. She was James' wife, and if James saw something in the future that affected their family, he would surely involve her. Also, Dumbledore might be in the story. He was always a key figure in the wizarding world, and James might seek his advice on what to do with his visions of the future.
Obviously, Naruto would be the main character since it's about his past seeing the future. Sasuke would also be important as Naruto's relationship with him is central to the Naruto series. Kakashi too, as he is Naruto's teacher and mentor, and his guidance might be influenced by Naruto's new - found knowledge of the future.