There is still two years to go for the bulk of the withdrawal, both can hold up to their respective stands for some more time, I figure there will be some sort of referendum in due time. Apology from US has its more intrinsic connotations the major being it will stop any kind of direct action from the NATO on Pakistani soil. If you see the build up to the Salala incident one can see that the NATO openly criticized Pakistan for the involvement of terrorists who attacked in Afghan soil. Their collective investigations and statements found that the terrorists attacked NATO/Afghan interests in Afghanistan and retreated back to safe havens inside Pakistan. The Salala incident happened bcos the NATO changed its prerogative and gave hot pursuit to the terrorists who were retreating into Pakistan and that the Pakistan Border force opened fire to safeguard them and they returned fire.
An apology takes away the option of acting against the terrorists and the frustration builds bcos they think that neither is Pakistani forces trying to stop this and when the NATO takes it upon itself to attack them they come under fire from the Pakistani forces. Anybody could be right here and wrong at the same time. Pakistan opening the route is the primary focus and the forces operating in Afghanistan is heavily dependent on this route.
A nation which has spent a half trillion in this war can spend a few more billion to go the CAR way, the worrying factor is after the withdrawal all of Pakistan's effort in the WOT will come to naught due to the last year's turn of events.