I understand your definition of winnable and gotta be honest, I don't think it's going to happen. It would be nice if it did, but to think it's a country, culture, lifestyle and viewpoint is going to change from that followed for centuries (if not thousands of years) just because a different group thought it up, is folly.
Kharzai stays as long as the Coalition stays, Coalition stays as long as Al Queda stays, Al Queda stays as long as they are a benefit to the Taliban. Taliban stays as long as....they hold both sides of the border? They keep their local villagers under their thumb? They keep the drug trade alive and kicking in the face of Coalition attempts to get rid of it. You name it, A-stan is in the middle of one very convoluted place with a ton of people on all sides throwing their .02 in. Trying to get a hold on it is like trying to grab jello.
I hope your right Colin. Hope they pull it off and the taste of modernity, coupled with Coalition efforts, support of Kharzai, ect, ect, helps turn it towards a more modern outlook. But with the majority of the people illiterate, indifferent and probably looking at the Coalition as just the next round of foriegners bucking up the newest Govt, I definitely have my doubts.