By reading a few of the comments here it seems our common folk like to think that they know more about what PAF needs to do than those professionals in the PAF itself.
What we need to understand is that we are cash strapped, US congress did not block us from buying those f-16s they just asked us to foot the whole bill by ourself, and we don't have the cash to do that.
And even if somehow we do get the cash (lets say Dar becomes a lannister and start shitting gold) what other options do we have.
Russia will not sell us SU-35 no matter how many times we write about it on this forum unless of course Putin becomes a member of the defence.pk and sees our enthusiasm, get impressed and with tears in his eyes allows us to buy those planes.
Rafale is not an option as India is already getting it and we can't afford Euro-Fighter even with that gold that Dar shit.
So only other feasible option is J-10 which pretty much offers the same goodies that a MLUed F-16 has to offer but will require the seting up of new infrastructure, training and doctrine and that too for just a couple of squardons.
Also please keep in mind that we need to replace about 200 old planes (read obsolete), and we need to do it quicky before we start having our own flying coffins. The pace at which JF-17's (which cost us correct me if I am wrong $30-35 Million each) leaving the assembly line it seems impossible that we will be able to replace all of these planes by even 2025. So if we don't procure alternatives we will lose quite a few of our brave pilots flying those junk planes.
Now getting these old F-16s for less than 20 Million USD a piece is a good bargain, once MLUed which of course will have its own cost these planes can provide 4000-6000 hours to PAF. So they can easily serve us till 2035.