Not only Pakk but even big powers shall not be able to replace their entire fleets of 4 th & 4.5th gen Jets entirely for long period of time. So Pak can't entirely go for only J31 rather we may have mix of 4th, 4.5th gen & 5th gen fighters. So if Pak may still go for J10b fighter jet with AESA radars. Further PN is in desperate need of long range fighter jets like J16 or J15 though in limited numbers to maintain some sort of deep naval strike capability which we can't achieve by our current Mirrage V fighter bombers.