J-10 is an excellent aircraft when coming with IRST and AESA, two things that PAF lacks. See, PAF seems to realize that a 250 BVR fighter force (100 F-16s possibly and 150 JF-17s) is too little for the needs of the region. We need 350-400 fighters. A lot of Mirage and F-7 squadrons need replacement, meaning you have 250-300 jets that need to be retired ( currently, the JF-17s have only managed to replace A-5s, which weren't in the Multirole Mix anyway). Now a common discussion on this forum has been that they will not be 1 on 1 replacement because JF-17 brings quality so numbers are not needed. However, think about this, it takes a lot of time and training and logistics to stand up a squadron. If you are not replacing 1 on 1, then it means going from 400 combat jets to 250 would mean that around 6-8 squadrons are now no longer needed. You will have to disband them. What happens to their infrastructure, manpower and above all the ORBAT?
It is not like if we need more in the future we can simply start another squadron. You lose out on skills, training and time. So it makes sense to make it a 1 on 1 replacement as much as possible. And that is where a few squadrons of J-10 can help.
Another issue is that JF-17 carries only 7 hardpoints, with 3 fuel tanks, that leaves only 4 outer pylons for BVR and WVR missiles. J-10 doesn't suffer the same handicap. You can carry more missiles and or strike weapons. J-31 is still 5 years away from any meaningful debate. So if PAF went for J-10s i wouldn't be surprised.
What i mean to say in short is that a 250 BVR force might be superior to the 400 aircraft non BVR force, but then the needs of the region have changed as well. India is not going to stop at replacements, they will eventually go for the 40 squadrons mark in the next 15-20 years. A 400 BVR fighter force guarantees an ample deterrence, and if and when PAF decides to field 5th Gen, we will have some JF-17s and F-16s (read MLU units and Jordanian) retiring as well, so we will have space to absorb J-31 or whatever automatically.