Perhaps he would find that the wizarding world has finally united with the Muggle world in harmony. Technology in the Muggle world could have influenced magic in strange and wonderful ways. He could be shocked to see flying cars that are now common, or houses that are built with a combination of magic and advanced Muggle construction techniques.
He could meet his future self. This would be a very interesting encounter as he could learn from his future self about what he has accomplished and what mistakes he should avoid. He might also meet the future generations of his family, like his grandchildren or great - grandchildren.
Well, Harry could be really confused at first. Ouran is a very different world from Hogwarts. He might be shocked by the opulence of Ouran Academy and the strange club system there. Maybe he'd try to find a way to fit in while still being true to his wizard self.
In this fanfiction, Harry might see a world where magic has evolved in ways he couldn't imagine. Maybe there are new spells and potions that are far more advanced. He could also encounter the future versions of his friends and enemies. For example, he might find out that Ron has become a very important figure in the wizarding world, or that Voldemort's influence still lingers in some unexpected ways.
Well, he might see some amazing technological advancements. Maybe flying cars are everywhere and houses can move. He could also meet his descendants and see how his family has grown over the years.
He could meet the descendants of his friends, like the grandchildren of Ron and Hermione. They might show him around the future wizarding world and tell him about all the changes that have occurred. Also, he may run into some new and powerful wizards who have emerged in the future and learn from them about new magical techniques.
He might meet international aurors. These are highly skilled wizards from different countries who are experts in dark wizard catching. They could teach Harry some new combat spells.
He could meet Fleur Delacour's family. Since Fleur is from France, her family might be an important part of the French wizarding community that Harry interacts with.
Hermione would be a likely companion. She loves learning and exploring, so she'd be eager to go on a traveling adventure with Harry. Ron might also tag along, especially if there's a chance of food and adventure. Neville could be another option. He has grown a lot in courage and his knowledge of plants could come in handy in different magical environments. Luna Lovegood would be a very interesting companion too. Her unique perspective on magic and the world would add a lot of fun and mystery to the journey.