Red Bull are in it for the brand recognition, and have always been quite open about the fact that they'd ditch the sport if they couldn't win or at least compete with a chance of winning. If they're looking to leave then it will be either because they don't feel that they can compete, or because the F1 audience is not aligned to their own customer target market. The latter would be an interesting reason, as it would effectively be a vote of no confidence in Liberty Media's plans to broaden the appeal of the sport.