I would suggest you re-assess your current situation and try to get objective answers of the following questions: who is most trusted person your boss consults with when he makes a decision? When someone in your group needs some help, who is the first person he usually go to? In your group who is the most well known person by other groups' managers, your clients and your boss's boss? From you boss's perspective, if he needs to start a new project that no one has done before, who will he pick as the project manager? If the answer is not "me", I think that you should forget the other guy and focus on self-improvement.
Another thing that you should be aware of is that every promotion is a well calculated move. A manager can tell who to promote if he needs to promote one person and who to let go if he needs to downsize, in less a second. And promotion is usually well communicated among your manager, you manager's manager and managers at the same level of your manager, way before the promotion actually takes place. Before you get your promotion, most times you already know which managers support you and which ones have doubts on you. So if you feel that you are ready to move up and lead a team, you should talk to your manager about your promotion and get his support and his boss's support. Do not wait for the other guy to fail and hope that your manger will pick you, it doesn't work this way.
Hope that helps a bit.