There's no way to know precisely without reading the 'watching the future fanfic'. But generally, there could be a group of friends or comrades who are facing the challenges of the future together. One of them could be a leader - type character with strong leadership skills. There might also be antagonists, perhaps those who want to control the future for their own selfish gains or those who oppose the positive changes that the main characters are trying to bring about.
Well, it's likely that Eren would still be one of the main characters. After all, he's a central figure in the original 'Attack on Titan' story. He might be the one most affected by seeing the future and could play a crucial role in trying to change it.
I'm not sure specifically as it depends on the fanfic. It could be new characters created by the fanfic author who are descendants of the well - known Star Wars characters. For example, a grandchild of Luke Skywalker might be a main character, carrying on the Skywalker legacy in new ways.
There might be an old sage - like character who has a vast store of memories and uses them to mentor the younger characters in dealing with the future. They could provide wisdom based on past events and how they might repeat or change in the future.
There could be the descendants of Jon Snow and Daenerys Targaryen. Their child might be a central figure, having to deal with the complex legacy of their parents. With the blood of Stark and Targaryen, they would have a unique position in the power struggle.
The main characters would likely include Ichigo, as he is the protagonist of the original series. He might be facing new challenges in this future scenario. Renji could also be a main character, as his relationship with Rukia and his own growth arc make him an important part of the Bleach universe. And Aizen, even though he was a villain, could play a significant role if the fanfiction explores his possible return or his influence on the future events.
Since I don't have specific details about this 'reading the future fanfic', it's hard to say who the main characters are. It could be the ones who have the power to read the future, or it might be the people around them who are affected by this ability.
Since I haven't read the fanfic, I can't say for sure. It could be original characters created by the fanfic author, or it might feature characters from an existing franchise that the fanfic is based on.
The main characters in 'children of the future fanfic' could be children from different social backgrounds. For instance, there might be a poor orphan who discovers he has the ability to control time, and a rich kid who uses his family's advanced technology to help the group. There could also be a young scientist - in - training who is trying to figure out the secrets of the future world and is leading the other children in their adventures.
Most likely, Marty McFly would still be one of the main characters. He's the central figure in the original movies and would probably play a major role in the fanfic set in 2015. Doc Brown would also be there, as he's the inventor of the time - travel technology and Marty's mentor. There could also be Biff Tannen or his descendants, as they often cause trouble in the 'Back to the Future' universe.
Obviously, Luffy would be one of the main characters. He's the captain of the Straw Hats and the central figure in the One Piece world. His actions and decisions would greatly influence any future scenarios.