UPDATE: Flightblogger was informed that Boeing will only add two 787s, ZA101 for ground testing and ZA103 for ETOPS testing. The other 2 aircraft will not join the flight test program and will be preparing for delivery.
Word just got to me that first flight of ZA006 is now delayed to September 24th according to Boeing's newest schedule. I'm still trying to ascertain the reason for the delay.
Additionally, according to Flightblogger, Boeing is adding 4 more 787 from the production run to aid in the test flight program. Airplanes 7 through 10 (ZA100, ZA101, ZA102 and ZA530) are to join the flight test program in order to ensure that the current schedule is maintained. All four airplanes are to be equiped with the Trent 1000. The first three airplanes are destined for ANA while ZA530 is for LAN Airlines. According to Flightblogger, these aircraft will have minimal instrumentation needed for flight testing and will be used mainly for ETOPS flights as well as functionality and reliability testing. I do also believe that the performance of the production aircraft will be compared to the flight test airplane performance.
Flightblogger: Report: 787 test fleet to grow from six to ten