Fan Speculation in the Chicago TribuneNews
The Chicago Tribune has a story (for their registered users only (registration is free)) featuring submissions by readers, proposing what the rest of the paragraph that begins with the released sentence from OoTP in which Dumbledore asks Harry to sit down so he can tell him "everything".
They also listed some common speculations:
Family ties. Most of you want Harry to be Professor Dumbledore's grandson and for Lily and James Potter to be alive. Plus, there's great interest in creating a long-lost sister for Harry (lots of you tried to figure out a way for that girl to be Hermione).
Star Wars. Lord Voldemort kept popping up as Harry's father, grandfather, uncle or some other blood connection. A few said he was Dumbledore's relative gone bad.
Hogwarts Heirs. Harry pulled Godric Gryffindor's sword out of the Sorting Hat in "Chamber of Secrets," which led many contestants to speculate Dumbledore confirms Harry is Gryffindor's Heir and must battle to the death with Slytherin's Heir (Tom Riddle/Lord Voldemort).
Fawkes the Phoenix. Most people linked the mysterious Order of the Phoenix to the fact that Harry's wand contains a tailfeather from Fawkes the Phoenix -- as does Lord Voldemort's wand. A good number of contestants remembered what Mr. Ollivander said: The wand picks the wizard.
Romance. James loved Lily. No, Snape loved Lily. No, Voldemort loved Lily. And Dumbledore was once married. No, he is dating Professor McGonagall. Cho Chang's mother is an evil supporter of Voldemort, and Harry should stay away from his crush this year.
People who aren't what they seem. Harry's parents have become phoenixes. James and Lily Potter were Death-Eaters. Arthur Weasley is a Death-Eater. Ron and Hermione are Voldemort's spies. Draco Malfoy is Harry's brother. Petunia Dursley is a witch but won't acknowledge it.
Too bizarre to categorize. Hagrid is Harry's mother. Dumbledore is Hermione's boyfriend (and he's also seeing Professor McGonagall). Dumbledore is a robot assassin sent to kill Harry. James Potter cloned Harry, and Dumbledore has a tiny Harry clone in a jar.
The winning entries are here, and the special awards for creativity went to these ficlets. The special awards for humor or satire are here.