Don't count your chickens before they hatch! If you think all's going to be hunky dory for Pakistan after the U.S. leaves, you're sadly mistaken. The real chaos will commence then, what with conflicting interests of countries that would want a piece of the cake. The countries with enormous stakes in Afghanistan include Iran, The CIS republics, China, Russia, India, and The US of A. And with each having an agenda of their own, it will soon degenerate into a chaotic civil war with a myriad war lords and regional players gunning for domination.
If Pakistan and more-so its army think that Afghanistan will soon become a cosy little Pakistani protectorate or a staunch 'ally', they've got another think coming!
There's no black or white in the geopolitical game.