Well, for the Avengers, it depends on the nature of the future shown. If the future is full of chaos and destruction, Captain America would likely feel a great sense of responsibility to prevent that from happening in their own time. He would start formulating plans and strategies right away. Black Widow, on the other hand, would be more cautious. She would analyze every detail of the future situation to figure out who the real threats are and how to neutralize them. Hulk might be confused and a bit scared at first, especially if the future technology seems like it could be used against him. But then he might see opportunities to use it for good, if he can get over his initial fear.
Well, they might be shocked at how much technology has advanced in the future depicted in the fanfiction. Maybe there are new types of elemental powers or different ways of training ninjas. It could also be that the relationships between characters have changed in unexpected ways, and they would have to come to terms with that.
They might gain a new perspective on their own abilities. If the future fanfiction shows ninjas with enhanced powers, the past characters could start to think about how they could develop their skills further. For example, if in the future they can combine elemental powers in new ways, the past ninjas might start experimenting.
In the 'rwby reacts to the future fanfiction', RWBY might have a range of reactions. Ruby could be full of curiosity, eager to learn more about what the future holds for her and her friends. Weiss might initially be skeptical, analyzing every detail to see if it's plausible. Blake could be more reserved in her reactions, quietly taking in the information while being a bit wary. Yang, on the other hand, might be more vocal, either expressing her approval or her doubts loudly. They would all be influenced by their own personalities and experiences up to that point in the story.
He might be shocked. In the fanfic, if he sees things like his friends' future achievements or the new threats that emerge, it would surely startle him. For example, if he discovers that one of his friends has a family of their own and has become a great leader in the village, he would be proud but also a bit surprised at how much has changed.
The X - Men might have mixed reactions. Professor Xavier would likely be intrigued by the potential for better mutant - human relations in the future. However, Wolverine might be skeptical and on guard, fearing that the future holds new threats to mutants. He's always been the more cynical of the group. The different reactions among the Marvel characters would add a lot of depth and interesting plot points to the fanfiction.
With his usual determination. Naruto has always been one to face difficulties head - on. So, even if he's shocked by what he sees in the fanfic's future, he'll likely try to find solutions immediately.