Any fighter that has served you for this number of years can't be a stop gap measure , this is even evident from the fact that paf opted for f-16s even after the embargo was lifted in early 2000s and paf had options from France Sweden and Britain to pick from .. There are other considerations as well like we can't afford Rafael and EFT besides they are also quite prone to embargoes with the French option has some leverage based upon retrospects but still . besides as paf is always looking to up the numbers of f-16s may it be by buying used ones or exercising the option of new one ...the fact is paf is going to do similar to what they did with mirages back in times...all of that because paf considers f-16 their front line fighter against Indian modern jets since jf-17 hasn't evolved that much and we still know avionics wise jft is not at par with block 52 ..so until any other 4.5 or 5th generation fighter gets inducted in significant numbers f-16 will remain your front line fighter ...the only thing that can save us this time is paf sourcing enough surplus/buffer spares that keeps f-16s flying even during hard times