Frankly speaking, their airframes are getting too old. They'll still be used as strike platforms for standoff munitions. Their naval role will be reduced due to availability of the JF-17 and more weapons package that come with it. Mirages will become ground support (Cluster munitions) and strike platforms for standoff weapons. If the PAF can secure more F-16's like 50 or so, you might see some Mirages start to phase out right away
Well, Israel is still selling old Kfir frames after upgrading them with lots of modern tech. As long as you replace parts there is not really an old frame.