In order to help module developers who are attempting to port their modules early enough in the D8 cycle to provide Developer Experience feedback, as well as to enable accessibility and usability testing of Drupal 8 against a non-moving target, we will be issuing approximately monthly alpha releases!

Since Drupal 8.0 Alpha 4 was released on October 18, we plan to release Alpha 5 on November 18, 2013. Use the alpha target tag to view a list of important issues we're targeting to get in by that time which you can help with!