So, at least 26 units have been manufactured. Possibly 52 based on two production lines working at approximately the same pace. Let's see what's the highest serial number this time next year?
I think we really ought to try to stick to the facts here Bub, 20-26, very possible, even quite likely,,,, 52 based on two production lines?? (for what its worth the Chinese usually do not have a production line, but produce in small batches), there's no real anecdotal evidence to support 52 completed aircraft at present??
and to address the nacelles, the aircraft had the inlets reshaped around the time the production version appeared, so yes, they will run the AL-31's and WS-10's until the WS-15 appears, and at that point new production aircraft will likely get the first engines, unless they choose to modify/test on an older tried and true airframe... I would suspect they will modify an existing airframe, but it might make more sense to test on a new airframe that did not require modifications