Realistically, I don't see Pakistan lasting beyond a couple of decades. Forget about everything else, it's their population that's going to destroy them. They are expected to hit 400M by 2050 and they simply don't have the resources to sustain that population. The resulting food crisis alone will kill them. They're already importing massive amounts of flour btw
It will more or less resemble Syria/Somalia with various non state actors taking control and tearing each other apart.
In fact, I'd argue that the whole reason Pakistan even survived till now is due to 2 important events. The first being the Soviet invasion of Afghanistan and the second being the global war on terror. Both wars allowed them to whore themselves out to the Yanks and receive 100's of billions of aid $$ for many decades
Their only trump card is providing some kind of access to Afghanistan, either their airspace or through some other means. That's pretty much gone now with with world having given up on Afghanistan.