You don't need the actual ATP by August. After that date you will just have to present the course completion certificate in order to take the written. If you already have the written you are good for 24 months. At least that is how I read it. Someone correct if I'm wrong.

61.153(e) After July 31, 2014, for an airline transport pilot certificate with an airplane category multiengine class rating or an airline transport pilot certificate obtained concurrently with an airplane type rating, receive a graduation certificate from an authorized training provider certifying completion of the airline transport pilot certification training program specified in §61.156 before applying for the knowledge test required by paragraph (g) of this section;