Roxy: Yes, we've been proven wrong, but that was at the beginning of the franchise before it grew into what it is today. Now, the books are all written. The movies are almost all out. Once that's out, there won't be anything to report on and as people grow up, we grow out of Harry Potter. We were with Harry Potter from start to finish (some of us growing up on it), but the kids in five, ten years won't be nearly as into it because it won't be the big thing at the time. The older people who were around when it was big will continue to like it, but it won't be that big of a hype. When the final book was released, there were more movies to be made and seen. After that, there's nothing more to release or you risk ruining the franchise. I must disagree with you. I don't think JK Rowling will continue it, as she's more about the series than the money she's making. I honestly think this fad is done with (coming from a massive Harry Potter fan). And concerning growing up with it, kids will never be as into what their parents were growing up as much as the modern stuff and the media hype won't be surrounding them.
Frogki: I'll have you know I'm in high school, and have been extensively been studying greek mythology since sixth grade. I'm a junior currently. Children's Book should be the first thing to set off a flashing light in your head. The kids growing up in a few years won't be surrounded with Harry Potter in the media because the movies and books will be over with, and will grow out of it like many hyped childrens books. Part of the reason it stuck with us is because we've ridden along on the journey. Mythology appeals to people as they grow into adults and it sticks. Whole professions are made off of it's study, which is more than you can say for Harry Potter.
Surveys aren't always put out with exact ideas in mind. For example you might put Disney Princesses in the survey to find out that people are drawn to more pink, girly, princess-like things, not necessarily that they're going to buddy up with Disney and expand the park that way. They could just be seeing how people feel about an expansion period and you don't know how other people answered that survey. For all you know, everyone but you was against expanding into the Lost Continent.
Concerning the arches, I lived in the UK and have no idea what you're referring to. I've also studied British architecture. How familiar are you with British arches?