Marty wakes up the next morning and at first thinks he's just had a nightmare. Until he notices that his house looks completely different, and that every member of his family is now a together, successful human being.
Oh, and the family car is just fine. In fact, Biff is out there waxing it right now.
A package arrives, and it's the first copies of George's new science fiction book. Looks like someone talked him into pursuing his dreams many years ago.