The founders might be quite surprised by the Golden Trio. They could be impressed with their skills and knowledge. For instance, Hermione's vast magical knowledge would surely catch their attention.
In fanfiction, when the Golden Trio meets the founders, there could be a lot of magic exchange. Maybe they'll learn ancient spells from the founders. The founders might be impressed by the Trio's courage and friendship.
They'd probably start off being really cautious around each other. The Golden Trio would be cautious because the Winchesters seem so different and rough. The Winchesters would be cautious as they're not used to this kind of magic. But then Hermione might start asking questions about the Winchesters' hunting methods and Dean would start joking about the Trio's school - like magic.
The Golden Trio's reactions would be diverse. Hermione would immediately start making mental notes about the new magic education system. She would be interested in how they teach Charms, Potions, and Transfiguration in the future. She might even try to get involved in some of the classes as an observer. Harry would be looking for the sense of community and camaraderie that he had at Hogwarts. If he doesn't find it in the future's system, he would be disappointed. Ron would be a bit overwhelmed by all the new gadgets and advanced magic used in the teaching process. He might long for the simpler days at Hogwarts, but at the same time, he would be curious about the new things he sees.
Harry's brave and sometimes impulsive nature might mesh well with James's boldness. They could be like two peas in a pod, getting into all sorts of adventures together. Hermione's intelligence and rule - following side might be a bit at odds with the Marauders' mischievous ways at first, but she could also learn to loosen up a bit from them. Ron, with his loyalty and sense of humor, would probably get along great with Sirius, who also has a strong sense of loyalty and a great sense of humor.
They might be really surprised. Harry could find it strange to see different versions of his own story. Hermione would probably be critical at first, analyzing the plot holes or inaccuracies compared to the real events. Ron, on the other hand, might find some of the more comical fanfictions quite hilarious.
Their relationships could develop in many ways. For starters, Harry might look up to James as a father figure he never really got to know. James, in turn, would be proud of his son. Sirius could become like an older brother to all three of the Golden Trio. He'd be protective and also share his wild stories with them. Remus would be a great source of wisdom for them, and Hermione would especially appreciate his knowledge. Ron might be a bit in awe of the Marauders at first, but soon they'd all be joking around like old friends. The relationships would likely be based on mutual respect for their different skills and the common goal of making the wizarding world a better place.
He might be initially shocked but then feel a sense of honor. After all, being chosen by the founders for a mission is a huge deal.
Well, in the future they could encounter different versions of themselves or their descendants. Maybe they would find that Hogwarts has changed a great deal, with new spells being taught that were unimagined in their time. And they might have to face new dark forces that have emerged over the years, using both their old - school magic knowledge and learning new ways to combat the threats.
Salazar Slytherin might be initially suspicious of Harry. He's very protective of his pure - blood ideals, and Harry being from a different time with different views could be a threat in his eyes. However, if Harry shows great magical ability and a deep understanding of magic, Slytherin might grudgingly accept him.
The time travel could put some strain on their relationships at first. Harry might be more focused on seeing his godfather again, Ron could be a bit jealous if Harry's attention shifts too much, and Hermione would be constantly worried about the rules of time travel. But as they work through these issues, they'd likely come out with a deeper understanding and respect for each other. They'd also have to hide their true identities from the people in that time, which would require a lot of trust among them.