Brian Fishman just bucked that narrative. He's written pretty much the most specific prediction of what will happen in Afghanistan over the next 10 years that I've seen so far. Believe it or not, it all comes down to U.S. foreign aid and Afghan fiscal policy, and it ends in a resumption of civil war:
The dependence on foreign aid to sustain political accommodation constitutes a “corruption paradox” in Afghanistan: the misappropriation of international assistance lubricates the implicit political covenant holding the current Afghan government’s coalition together, but it also advances the failure of that Afghan government in the long-run by preventing the state from developing a viable revenue structure...Fishman estimates the total cost of the American strategy in Afghanistan post-2014 will be something like $15 to $25 billion, with maybe a little help from our allies. The foreign assistance component will not be disbursed any more efficiently than what has been disbursed so far; if it were distributed properly, presumably, then the Afghan state would be forced to develop its own domestic revenue sources, which would mean taxing its own citizens, which would force it to become more accountable to its citizenry, which would make it ultimately more democratic, less corrupt, and stable.
In the medium- to long-run, fiscal unsustainability and aid dependence is a recipe for state failure and civil war in Afghanistan. That, rather than the Taliban, is the most important threat to the Afghan state, particularly because political consensus favoring assistance to Afghanistan in donor countries is likely to crack when most troops come home in 2014. As they do, domestic pressure in donor countries, including the United States, to reduce the amount of aid to Afghanistan will increase. Aid is likely to fall. In this scenario, the Afghan government, still unable to generate sufficient revenue independently, will not be able to support governance measures outside of the security forces; warlords will have less incentive to tolerate power sharing and the authority of Kabul. Afghanistan will likely return to civil war.
That conclusion is essentially independent of any judgment about the strength of the Taliban, the effectiveness of the Afghan National Security Forces relative to its enemies, or the wisdom of various local security programs, such as the Afghan Local Police. Debates about these issues play an overly large role in policy discourse about Afghanistan.
Students of modern Afghan history will note that Fishman's prediction for Afghanistan post-2014 is more or less exactly what happened to the Soviet-backed Afghan government, the Democratic Republic of Afghanistan, post-1989, as Fishman explains in the article, hence the title "Russian Roulette."