Haven't really read or watched any interviews for some time so can not comment but my own opinion is Block 4 or 5 will not be on the cards as PAF would be looking towards Project AZM.I don't have any inside info , but if we look at different news about JF-17 , different interviews of ACMs this all point out in one direction We might see more then 3 blocks …. Just look at JF-17-B , is that not another block
(people talking about JF-17 glower) .. Rest time will tell .
Also reaching the target of 250 aircraft would take PAF around 2025-26 where stealth aircraft would be available to replace other PAF assets.
PAF also requires LIFT platforms and is not looking towards JF-17 to fulfill so this indicates that PAF would be procuring something from the market most likely Turkish Hurjet which would be mature by that time.