One thing apparently seems clear that US is not ready nor can afford to leave Afghanistan at all. It seems like US/NATO will privatize Afghan War through Mercenaries as they wouldn't leave this Buffer-Zone unattended rather will try to expand disruption throughout the region or at-least in Afghanistan possessing big threat to all neighboring countries.
Afghanistan holds importance in this region for western allies to keep their presence & fueling unrest which can help them to escalate civil wars, terrorism or private war against Rivals especially Russia, China & Pakistan and try to engage them to exhaust.
Iraq & Libya are clear examples in this regard that after initial invasions in the name of so-called democracy/liberation & war on terrorism, the peace has never returned nor NATO left the country except for the losses for Civilians on top.
There have been talks regarding possibility of Privatized War through Black Waters and then, as it is observed that even UK G4S is already present on ground in Afghanistan. Analytical view of situation suggests that US/NATO are already building tactical sites in Afghanistan which clearly indicates about larger scale war in up-coming days. However, Afghanistan ruling party does not want any peace or at-least compromise with Taliban which is actually a threat to all sort of corruptions by ruling elites at the moment that empowers warlords to the fullest either part of Government or outside.