I first saw this on Twitter a few days ago as a retweet from Pottermore. Jason Kottke has the best summary of it I could find:

In a piece for the Pottermore web site, JK Rowling writes an update on how the gang from the Harry Potter books is doing. The piece is an account of the Quidditch World Cup Final written by Rita Skeeter, the gossip columnist from the books. You need a login to read it on Pottermore, but someone uploaded it to Reddit as well.

That last line is one of a few references to possible new stories in the piece...the last paragraph mentions a new biography of Harry and his pals due out at the end of this month:

And for those who want to know exactly how imperfect they are, my new biography: Dumbledore's Army: The Dark Side of the Demob will be available from Flourish and Blotts on July 31st.

Could Rowling be setting the stage for an eighth Potter book or is she just winding us up?

Very interesting. When I first read that myself I thought -- No...she couldn't have. But now that I think more about it...perhaps?