Recently, J-20’s 2016 aircraft appeared for trial, it’s basically the same as the 2015 prototype in appearance, but the bulge of air inlet has a different coating, and the ventral part seems to be improved in term of stealth.
The interval between 2015 and 2016 prototypes are nearly one year, and since there is no big difference, the technologies should be stable, and the production of prototypes might be ending. For next phrase, J-20 might be produced for air forces to try.