Re: New Generation Fighter
The tech gap between 4th generation fighters and 3rd generation fighters is the largest among all fighters since WW2, probably comparable or even bigger than tech gap between 3rd generation fighters and 1st generation fighters due to stealth.
A J-20, lets say, with even J-11's engines and radars, are still way way better than J-11 in air-combat thanks to being stealth: internal military excerise between J-10 and J-11 show J-10 can beat J-11 easily (8:1), partially because J-10 can spot a J-11 ~15-20 km more than J-11 can spot a J-10 due to J-11's huge RCS, this gives J-10 a critical advantage such that they can make their plan to trap the J-11s.
And now replace J-10 with a stealth fighter and you can imagine the outcome.
Needless to say J-20's radar is highly likely being ready in time, the only part which lag behind is engine.
So when J-20 become ready (besides the engine part), there is no point to waste any resources on the last generation fighters, they will enter production with the downgraded engines, and when the more capable engines become ready, they will introduced them into their later batch of J-20s, just like the case of how Soviet handles their MiG-23 production.
Just during one most recent TV interview, a professor and major general of PLA's national defense university, openly said the priority for Chinese 4th generation fighters are (from high to low): 1, Stealth, 2, Networks, datalink and advanced radar and sensors/electrionics 3, Mechanical performance like supercruise and post-stall manuerves etcs.
Which just proved my points.