Right now, Pakistan has around 18 squadrons which field combat aircrafts including the F-7P/PG's, JFT's, F-16's & Mirage III/V Roses ...
Out of these 18 squadrons ... 5 are F-7 P/PG squadrons (3 PG squadrons & 2P squadrons), 6 squadrons of Mirage III/V Roses (Bandits,Haiders,Tail choppers,Cobras, Tigers, War Hawks, Eagles, Ghazis,Talons, zarrars & night srike Eagles)
The rest are JFT squadrons (Minhas, Black spiders & panthers) and F-16 squadrons (falcons, griffins, arrows,sherdils)
So let's get this out of the way ... Pakistan doesn't have to replace "300 aircrafts" -- it has to replace '11 squadrons '
A squadron strength may deviate from 16-20 .. with that in mind, if we look as to how many squadrons JFT block I has formed ... that would be 3 on a squadron strength of 16-17 (depending on how much JFT's we have in CCS)
Going by todays numbers of 150 on order = We have the replacement of 6 squadrons in the bag ... which squadrons are replaced ... well most likely the F-7P's will be first ... and going by how much PAF is interested in anti-ship weapons and stand-off A2G weapons ... JFT can also replace the Mirage squadrons ...
So, now we only have to worry about replacing 5 squadrons ... the current strength of the F-16's is 76 and it forms 4 squadrons of PAF, if we were to go by the initial target of 110 aircrafts .. we can form two more squadrons of F-16's.
That leaves us with 3 squadrons to worry about ... with the EEZ and CPEC, most likely a heavy multirole fighter, now it could be the SU-35 or a even a deal with both the Russians and Chinese to provide some "solution", or we could go for J-10C and if the financial crunch continues, induct more JFT block III ...
The J-31 would most probably replace the oldest F-16's if taken, so concluding ..
-PAF does not have to replace 300 aircrafts, it has to replace 11 squadrons and squadron strength can vary -- while out of these 11 squadrons, PAF has a set solution for 6 of them in the JF-17's
-Under ideal conditions, PAF only has to worry about replacing 3-5 squadrons
-The options that can fulfill this are many and will become more clear as we approach 2020 (most likely J-10 B/C, SU35 or J-11 series if it can become available for purchase)
-By 2020, we can easily have an airforce that is predominantly a 4th generation airforce
-With the upgrades of JFT coming up, and the number of weapons & options available,, JFT will surely be a force to be reckoned with
- If PAF wants to go for more falcons as its more cost effective, (the cost for infrastructure, training expenses etc. can be cut )it should opt to induct advanced weapons like the Aim-9X to make the falcon fleet alot more potent then it already is..
-If everything goes as planned, the disparity between the prowess of IAF and PAF will be the lowest since the 1990's ...