I've been counting down the days and hours until this moment, and now we finally know what it is!
Stop with the guessing! Now we know that Pottermore is a reading site!
Pottermore is an exciting new website from J.K. Rowling that can be enjoyed alongside the Harry Potter books. You can explore the stories like never before and discover exclusive new writing from the author. It is FREE to join and use, and is designed to be safe for people of all ages. [from Pottermore]
We'll be able to re-read the series and get new and exclusive data from the author. From what I gather, it'll be a sort of interactive site, where we'll read and share thoughts, and build the story as we want it.
"Follow the owl," Jo says, so I'm thinking HP-related sites will have owls scattered around them come October, and they'll lead us to new experiences from Pottermore.
We've waited for this announcement, but now we'll have to wait until October, too. Wow, it can't come fast enough.