A flurry of posts on COIN happen to form a coherent discussion of the strengths, weaknesses and future of counterinsurgency in the post-Afghanistan era: Michael Cohen here, David Ucko here, Spencer Ackerman (responding to Cohen) here and Andrew Exum responding to Ucko here. This last one by David Steven, unrelated to the rest, neatly wraps some context around them all.
As for me, I think the U.S. military will leave Afghanistan having integrated the full-spectrum, whole-of-government approach to warfare, that it will not reapply its newly gained expertise in any major conflict for the decade that Stevens floats, but that it will possess a virtual monopoly on the practical skill sets that will drive military-to-military training missions designed to stabilize conflict zones for that same period of time. In other words, COIN — and with it, the U.S. military — will remain practically relevant as the glue that binds America’s strategic relationships with weak states and lesser regional powers.