well PAF will have to make some hard decision and make them fast, in fact the only way forward i can see it to increase the number of Block 3 JF to 100 , and with them try to re-engage with US to get those remaining 18 F-16 block 52's .. I doubt US will be allowing us the " Viper " modification like Taiwan but getting 18 more block 52 with same config as we already have will give us some breathing space in any future conflict with India even with Rafale Throw in ..the other thing we can do is to create 3 layer Air Defense shield with HQ-9 or Aster blk-3 as LR-SAM, HQ-16 and SPADA-2000 as MR-SAM and FM-90 / Pasntsir as SR-SAM ..
Until the J-31 seen the light of day or final Prototype , All we can say is that, in any Future conflict with India , we have to be lucky all the time, but they have to be luck just once ..