Maybe you believe each book a children's writer writes should stand on its own merit, or maybe you believe that there surely must be a writer "out there" who can provide a successor (pun intended) to the Harry Potter phenomenon.
Whatever your viewpoint, take a look at this article:
"Publishers search to find Harry Potter's replacement" http://www.pe.com/entertainment/stories/PE_Fea_Daily_D_nextpotter22.1147b8f.html
Here you will see information on some suggestions of, one might say, "book life after Harry Potter."
Do you agree, or disagree, with the suggestions - or do you think there may be another writer's creation that could be the one that's successful after Harry?
Maybe its you who has a manuscript, or you who could write one, that could "fill the bill" or meet such "great expectations." Maybe its you who could even create a character that might be able to metaphorically "walk in Harry's (or Hermione's) (or Ron's) shoes," or in his/her footsteps, or beyond them, perhaps.
Ponder the possibilities. Maybe you have your own room full of secrets, or a magical gem, or _____ ... just waiting for you to wave your wand, and ....
Well, you get the idea now :)