J.K. Rowling also stated several times that there will never be any prequels, citing the disastrous Star Wars examples.
Honestly, I think Pottermore is akin to Y2K - much ado about nothing. It's probably just an interactive website for fans. All the hype likely won't live up to the anticipation.
Then again, who knows? Given the gal's massive imagination, anything is possible. As of this typing, all will be revealed in 4 days, 5 hours 10 minutes and 11 seconds. Tick tock.