I think it'd be part necessity, part feasibility and part necessity on the part of the PAF. While the sudden influx of surplus F-16C/Ds (with LESP and CCIP-like upgrades) can affordably and effectively meet the medium weight multirole fighter needs of the PAF, it seems the PAF itself is being a bit conservative with its approach to the U.S. While such F-16s would make great air defence assets, their strike capabilities wouldn't be at their maximum potential unless U.S releases JASSM, JSOW, etc. On the other hand, PAF can equip the JF-17 at will, but the maximum desired effect in any one engagement may not come about due to the JF-17's limited range and payload. Importing something like J-10B or J-31 may be too cost prohibitive if done in heavy numbets (suitable for a backbone fleet in the future).
5-7 years from now the PAF can take one of two options. It could pair up with an external vendor and develop an entirely new successor to the JF-17 and ensure, from the ground up, that this next gen fighter improves upon the JF-17 in every relevant respect. Or it can take what it has on JF-17 and develop a larger and lighter weight fighter capable of comfortably carrying more without greatly degrading performance. The 'JF-17 II' could be the next backbone fighter, but it'll depend on what route PAF takes. Personally, I'd rather they design a new jet from scratch