This shouldn't be a surprise to seasoned watchers. Unlike Apple, who control almost every part of the process from software design and coding to hardware construction, Microsoft have a huge number of partners at all levels that need to be aware of the plans for Windows Phone 8, and the Windows Phone Summit was a public way to being many of them up to speed with developments.
This release has a significant amount of new functionality for developers and IT pros in particular, and because of the planning cycles involved in getting them the information they need to take advantage of the release when it hits, we thought it was important to confirm and prepare them. Which is partly why we didn't detail all the consumer features.
Sullivan goes into some detail about Microsoft's thinking around the story of Windows Phone 8, and it's worth reading the full interview on Pocket Lint.