Your point is very interesting, on the one hand Pakistan can't afford to develop jf-17 blk4, but they want to equip 5th or even 6th generation fighter.
It is well known that fifth-generation fighters are characterized by stealth, over-the-horizon air combat, hyper-mobility and, most importantly, stealth. The sixth generation fighter is still under development, hypersonic may be a direction, directional high-energy weapons are also a direction, as well as artificial intelligence, air and space operations. Focus on variable cycle engines, low speed large bypass, medium speed small bypass, high speed scramjet. Different speeds require different forms, so chief engineer Yang said the sixth generation machine is Transformers.
So the question is, does the PAF have the money to develop the JF-17 blk4, or does it have the money to buy the sixth-generation fighter?
In my opinion, the pragmatic approach is the J-35 + JF-17 blk4.
Of course, OBOR mechanism will make Pakistan rich and it may be possible to achieve J-40 + J-35 combination in the future