Afghanistan has long been a proxy location for the conflict between Pakistan and India however that's not the whole issue. They have their own Taliban, the TTP, which, like the Afghan version, is a creature of the ISI. There is a powerful strain of fundamentalism in Pakistani society, predominantly in the Pashtun region, and it's not beyond the bounds of possibility that it will become stronger - particularly with an Islamic emirate on their border.
As for the range of possible venues for the "jihadi" diaspora to enact their fantasies, there are plenty available. However the example of an insurgency that has defeated 20 years of the USA's efforts to drag a primitive culture into the present is going to be an irresistible lure.
Although it's currently forbidden to acknowledge the fact, the whole problem of "Islamic fundamentalism" is inherent in the very basis of the religion.