Some teams at Ubuntu and in turn Canonical have already shifted in large part to using Ubuntu Discourse for long-form communications. Now a discussion has been initiated if Ubuntu mailing lists in mass should be transitioned to using Ubuntu Discourse.
Ubuntu developer Robie Basak has started the discussion over this possible transition from mailing lists to the Ubuntu Discourse for long form written communication. The idea is still being raised and some ideas will be hashed out over possible workflow changes for Ubuntu Discourse usage.
Those interested in voicing their opinions or following the conversation over moving from Ubuntu mailing lists to Discourse can see this mailing list thread for the new topic.