There is no MSN 6620 anymore, the production slot was canceled.
MSN 6464 was supposed to be the P&W A319neo testbed. After it emerged from final assembly, the pylon was changed to fit the LEAP engine. Airbus can change the pylon again to fit the P&W powerplant.
Well-well-well, it becomes even more intriguing.
So, I would like to put it clearly.
1. MSN 6464 was supposed to be A319neo/PW flight test article
2. MSN 6620 was initially planned to be A319neo/CFM flight test article
3. MSN 6464 was converted to be an A319neo/CFM flight test article
4. MSN 6620 is now cancelled
So, the A319neo/CFM will get its type certificate around mid-2018. And then maybe, just maybe. MSN 646 will be converted back to an A319neo/PW flight test article.
1. When will the first A319neo/CFM enter into service after its certification?
2. When will the A319neo/PW be certified?
So, what's the plan?
This is even more interesting than I initially thought.