Those Talis who have close ties to Pakistan will not lay down their weapons even after foreign troops leave as long as Pakistan feels, it doesn't have a friendly government in charge in Kabul. Troop withdrawal will at least tell which factions of the Taliban are ready to make peace and which ones want total power. Foreign troop presence is their excuse up until now not to lay down their weapons.
Possible but remember Pakistan supported Taliban because Kabul supported militants attacking Pakistan in the past. Taliban didn't accept durrand line but neither they supported anti-Pakistan elements. They stayed neutral, so if anything it's up to Afghan leaders. If they want to go back in time then Pakistan will support Taliban or for that matter ISI can come up with any organisation in Afghanistan. There is no shortage of unemployed Afghans.