In my humble view PAF wanted to cash on the clause that Pakistan can buy 18 more F-16s in addition to 80 Block-52s (The number decreased to 18 due to Earthquake 2005 and other financial constraints). The same clause is expiring soon and PAF wanted to make best use of it and ordered 8 of the them to augment already present 18. Now question arises about heavies and twin engine ones. So had PAF not been interested in heavies like SU-35 and J-31 then it would have surely ordered 18 or even more as we had bought only 18 out of authorized 80. 18 plus 8 makes 26. So it means that we have now got two complete separate Squadrons of Block-52s with each Squadron having 13 of them. And this also means that these are the last of Block-52s or higher for PAF as if at all they would like to go for another Block -52 or highers ones purchase then they had to wait for the new President of USA and new congress members etc etc. Which only means 3 plus years more wait and that PAF can never afford.
PAF is still on track after heavies like SU-35 or any Chinese Twin Engine ones and that is evident from CAS statement that we looking both East and West for next Gen Aircraft.
PAF is looking for a next generation fighter in both, east and west - ACM Sohail Aman
His words are enough to prove that these 8 are just augmenters and had PAF gone for higher numbers then it would surely have meant bye bye to SU-35s and others.
So we wait till we hear some good news about heavies.
It was my humble view to which seniors can add more.