In the future, Hermione could encounter a group of time - traveling wizards from an even further future. They could be on a mission to change something in the time she has traveled to. This would create a complex situation where Hermione has to decide whether to side with them or not. She could also meet wizards who have made it their life's work to preserve the old ways of magic in a future that seems to be moving towards more modern and unorthodox uses of magic.
She could meet her future self. This would be an interesting encounter as they could compare their experiences and knowledge. Her future self might give her some advice on things she should do or avoid in her own time. Another person she could meet is a descendant of her friends. For example, a grandchild of Harry and Ginny who has inherited their bravery and magical skills.
She could meet the founders of Hogwarts. Imagine Hermione having a conversation with Rowena Ravenclaw about the importance of knowledge and wisdom. She might also meet Godric Gryffindor and learn about the true meaning of courage from him. Another person she could meet is Salazar Slytherin. It would be very interesting to see how she would interact with him, given his views on blood purity.
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.
He could meet his future self. His future self might be wiser, having learned from all the experiences in the past. They could have a deep conversation about Shinji's purpose and the mistakes he's made.
She could meet her doppelganger. In the opposite world, it's possible that there is a version of herself with different characteristics or a completely different personality.
There's a possibility she meets a group of young Italian wizards and witches who are part of a secret magical society. They are dedicated to protecting the hidden magical places in Italy. Hermione gets involved with them and helps in their quests, while also learning a great deal about Italian magic and culture from them.
The plot could involve Hermione traveling to a future where the wizarding and muggle worlds have merged. She would then have to adapt to this new reality. She might see muggles using magic in some form, or wizards having to abide by muggle laws. This would be a huge change from what she's used to. Also, she could be on a mission to fix something in the future. Maybe there's a dark magic that's threatening to destroy both worlds, and she has the knowledge from her time to stop it.
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.
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.
In the past, Sakura could meet the original creators of the magic system she uses. They might be able to teach her things that have been lost over time. She may also encounter a young, talented artist or inventor who was never mentioned in the history books. This person could be creating something that will have a big impact in the future. And there's always the possibility that she meets a kind - hearted stranger who becomes her best friend in the past and has a lasting impact on her life, even when she returns to her own time.
She could meet Bella Swan. They might start off as a bit of an odd couple, with Bella's more reserved nature compared to Hermione's boldness. But they could learn a lot from each other.