The economy is still in recovery right now. Back before the earthquake, the acquisition plans looked promising but even they were calculated upon expenditure marked for approval upon the availability of future funding. The earthquake, the global economic meltdown, the years of terrorism and civil war, and the incompetent leadership have taken their toll on funding for new shiny toys.
But the fact that PAF is still interested in F-16 acquisitions and has gone through with 13 more from Jordan says something quite clearly; despite almost a decade on since these plans were fully laid out, PAF still sees more F-16s as a good bet, and it'll probably try to get as close as it can to meet the requirement given what funding is available.
That last part is important, keep the economy going on the upward trend, ensure political stability and then competence, you'll have your F-16s and more yet.