Excerpt from the site:
"There are now one million people with access to Pottermore and everyone who registered through The Magical Quill challenge can access the site.
The Beta is enabling us to learn a lot about how people want to use Pottermore – and to understand the features they enjoy the most.
Since the launch of the Beta, we’ve seen really high levels of activity, and interaction with the site has been phenomenal. This affects how quickly we can give everyone access. As a result, we’ve decided to extend the Beta period beyond September and take a different approach to the way new users are brought onto the site.
From the end of October, registration will be opened to everyone and we’ll be giving access to registered users in phases. Access may be granted quickly, but please note it could also take some weeks or months, depending on demand.
We are also making a number of enhancements and simplifications to Pottermore, in order to make the site smoother and more enjoyable - so existing Beta users will likely experience some changes when new users begin to join...."