It depends on whether the H-1B is approved as a change of status or not. If your prior status expires in September then it probably cannot be approved as a change of status since the earliest a H-1B can become valid is October 1, 2013 and there has to be uninterrupted lawful stay in order for the change of status to be approvable.
Answered on Jun 11th, 2013 at 10:31 PM