Thus far it's just an offer from Turkey, we don't know how the PAF will respond. That said, I am beginning to think that the next-generation fighter program is - at least initially - a replacement for the oldest F-16s. In that vein, it has to be high-performance, high quality, high-tech - it will form the future qualitative edge. For the backbone, we have the JF-17, and for the future, we would just have new version JF-17s.
As for Turkey, they'll benefit from another user, who will add to the TFX's scale and help distribute the overhead research and development cost. If Pakistan could further help by providing some lower cost manufacturing work in some specific areas, that would be great.