Pak should not worry at all it's just at papers at moment .it will take time probably years when the first plane will be roll out and PAF will looking to retire those planes we should better donate our retire F16s to our neighbour .
India is just a American pawn againest china nothing more as what Indian history is .
Pak always get top notch equipment from china depands where theior tech stands at moment .i see no issue for 5 th generation jet for Pak we have many option j20 even turkish TFX .India and China are too big to be enemies , at most they are rivals strategicly using smaller nations for geo politics.
Ex china : Pakistan, Philippines,nkorea
India : nepal,Bhutan,Afghanistan
Secondly, Pakistan isn't going get any subsidized 5th gen fighters in the foreseeable future.regardless of how close you think your relationship is with china , they aren't going to sell their top shelf arms witch are still in development.
Also India and Russia have a active 5th gen FGFA fighter program , in any case India can shell enough cash to speed up the development. Unlike Pakistan who can't afford it from their 7 billion $ budget.
India is just a American pawn againest china nothing more as what Indian history is .