Hermione Granger is often a central character. Her intelligence would be crucial in trying to understand and combat the dystopian elements. Harry Potter himself also features prominently, usually as a symbol of resistance against the oppressive regime. Draco Malfoy can be an interesting character too, sometimes he might be forced to choose sides in this new, dark world.
One common theme is the corruption of power. In a dystopian future, the Ministry of Magic might become tyrannical, misusing magic for control. Another theme could be the struggle for freedom. Characters would fight against oppressive laws and dark magic. Also, the breakdown of the magical community's values, like the importance of friendship and loyalty being forgotten in a harsh, survival - focused world.
No, Harry Potter is not typically classified as dystopian fiction. It's more of a fantasy series with magical elements and a focus on the adventures of the characters.
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.
He might meet the future versions of his friends like Hermione and Ron. Their children or grandchildren could be there, and they might have different personalities and magical skills compared to their predecessors.
He'd first have to get used to the new technology. If there are new magical devices, he'd need to learn how to use them. For instance, if there are advanced wands with extra functions, it would take him some time to figure them out.
He might be shocked. In fanfiction, the future could be full of strange twists. For example, if his friends' children are involved in some wild adventures that are very different from what he expects. He would probably be confused at first, then curious to understand how things got to that point.
One common theme is a darker, more authoritarian Ministry of Magic. For example, in some fanfictions, the Ministry might have extreme control over magic use, even dictating which spells are allowed and which are not. Another theme could be the subjugation of certain magical races, like the house - elves being treated even worse than in the original series. And the idea of Hogwarts as a place that loses its magic and becomes more of a prison - like institution for students, with strict rules and a lack of the sense of wonder it had in the books.
Harry would rely on his basic values. His loyalty and courage would still be his strong suits. He might join a group of young wizards who are working on some noble cause in the future magic world. Through interacting with them, he'd gradually understand the new rules and customs. For example, if there are new dueling regulations, he'd learn them in the process of joining friendly duels.