Those have been my Potter sentiments for years, but as you said "5-year olds don't have very high standards". To them, walking around a "wizard town" eating Jelly Belly's and drinking soda waving their toy wands is the greatest thing ever to happen.
Then those kids will grow up and either become normal people or real nerds, and us real nerds have Tolkien to obsess over instead.
Disney can essentially live forever on the classics like Cinderella, and Snow White, but with the quality movies Pixar has been adding we can hope they still have the imagination and energy to keep making wonderful new franchises that will fuel the parks for years to come. I'd love to see something new and exciting added to the parks, but lets face it, Harry Potter isn't the catalyst to drive those changes - they'll come on their own schedule.
Two cents spent.