I'd like to echo what a few of the posts above have said and to add support for the idea that Drupal Answers is kept on Stackexchange rather than being shifted to Drupal.org or becoming part of the official Drupal brand in some other way. I've used the various support options on Drupal.org - the forums, mailing lists, IRC, etc - for a number of years, and while they are all useful in their own way I've found Drupal Answers to be far, far superior to the Drupal.org forums.
Yes, new users will arrive at Drupal.org first, but I don't see why that is a reason for switching the functionality of Drupal Answers from Stackexchange to Drupal.org. Surely advertising Drupal Answers on Drupal.org would be sufficient.
Furthermore, I don't see why Drupal Answers has to be seen to be evolving to solve the long-running Drupal documentation problem. I don't think that was what it was intended to do at the outset, and writing or collating documentation is a highly-skilled and highly-specific task that requires specific thinking and specific tool sets. It shouldn't be seen as being an offshoot of whatever solutions we've got at the moment, especially when those solutions were never designed to solve the documentation problem. Drupal Answers provides a great service in terms of providing answers to questions, and I'd hate for that to be lost.
In short, if it ain't broke, don't fix it. That doesn't mean that a new project couldn't be started on Drupal.org to run in parallel to or in competition with Drupal Answers, integrating some of the features that have made Drupal Answers work as well as it has worked up until now.