PAF currently has:
76 F-16 (8 more on order given new deal, with possibility for potentially 10 more)--->Spares are said to have been acquired to keep the fleet running a minimum of 5 years without cannibalization.
70 JF-17
60 F-7PG (expected to serve into 2025)
125 F-7P
33 ROSE I Mirage 3
42 Mirage III (non-upgraded)
20 ROSE II Mirage V
14 ROSE III Mirage V
51 Mirage V (non-upgraded)
Realistically speaking, today PAF has only 146 Frontline Fighters. The JF-17 is being added to at ~16/yr and for now there are plans for 18 more F-16 (Total=94 with rumored plans of acquiring older models from international sources up to 110- 120).
Lets just deal with the 94 F-16s for now. We know that the eventual line (at least through block 3) will be 150 JF-17 (which at the current rate would require 5 more years to achieve at 16/yr). That gives PAF 244 front line fighters. Let us assume that as per plan the F-7PG are to serve until 2025 and the ROSE Mirages can also be lumped into that though 2010 was the supposed retirement timeline (meaning these may be airframes that are part of the 190). That adds 127 Fighters bringing the total number to 371 which is right smack in the middle of the number the article states the PAF wants (350-400 fighters), so while 190 jets need to be replaced (I think the ROSE Mirages will go before the PG given that the PGs are newer airframes), there are a total 218 fighters that need to be phased out (non-upgraded Mirages and F-7P) and this will not likely be done on a 1:1 basis. 80 will be overtaken in next 5 years by JF-17. Lets add the 67 ROSE Mirages in which do need to be ~1:1 to maintain battle efficacy so you are looking at the need to fill a total of 147 airframes (80 for sure with JF-17 and 67 unaccounted for). You want to throw the PGs in there and that will slightly overtake the 190 number (but really the PGs are point defense fighters and would not need 1:1 replacement.
The Critical number is 67 which are currently unaccounted for ROSE Mirage Replacements.
That makes looking at this much more manageable. There are a number of ways to fill that number including the dreaded prospect of more F-16.
F-16: As
@Quwa has stated in the past, older model F-16 A/B ADF/OCU which can use AMRAAM. Potential Sources for more F-16s:Venezuala has 21 F-16 that it is unable to operate. If these are acquired it would give PAF 117 F-16s (all AMRAAM capable). Jordan may sell off more older model F-16 but the ideal solution would be the Venezualan F-16s
Su-35:Is a possibility depending on talks with Russia. Provided the PAF has the $$, these are potential fighters which would be very beneficial for the PAF and would be the most advanced fighters in Asia in active service (along with Russian and Chinese Su-35). Up to 40 of these would be beneficial and potentially doable.
JH-7B: Would be needing electronic modifications with AESA radar (hopefully from J-16) and IRST but would be a low cost alternative to Su-35 and would be an Ideal strike fighter to supplement both PAF and PN needs
Typhoon: A costly but politically doable option. The funding would be astronomical and likley prohibitive but if a deal for 40 air frames were able to be worked from a financial standpoint, this would be the best solution.
Rafale: Given IAF is purchasing these, they seem unlikley, BUT if the IAF deal falls through (unlikely) then they are again a possibility, but the same issues as with Typhoon.
J-10C: Would be a potential solution given the issues of sanction happy US congress, coupled with the need to acquire a large amount of airframes quickly. If PAF is unable to acquire an additional 20-30 F-16 then the J-10C becomes a very real option, but it is NOT ideal. It would put the J-10C right in the middle of the JF-17 and F-16 in terms of physical capability, while electronically superior to both (though the Block 3 would likley be roughly equivalent). It operates in too many overlapping ways with the already large F-16 and JF-17 fleets and in that sense would be redundant. Only possibility of these entering PAF service is the need for a large number of airframes in a short period of time, and I think the PAF would rather have the ROSE mirages soldier on until more JF-17s are available than commit to a 3rd platform of similar capabilities to the other 2 in service.
Su-35 would be the ideal addition, short of that, more F-16s (unfortunately for PAF) are the most likely solution until a 5th Gen platform like the FC-31 enters service and starts to replace older block F-16s. The JF-17 will continue to be upgraded and, I very much agree with
@MastanKhan that the model needs to be given the F-2/Gripen NG/Super Hornet treatment by scaling the design up 10-15%. This will allow the PAF to fit a much improved engine (like AL-31/AL-41 in place of the RD-93) and more hardpoints. Give it better RCS reducing features and you have the ideal F-16 replacement with a potential of ~7500-8000kg worth of payload and 9-11 hardpoints with integrated IRST and chin hardpoint for pods. This along with older variant JF-17s could serve with 60-80 (long term) FC-31 to form the fleet going past 2030-2040.