His goals are fairly modest:
While this will undoubtedly be a long and difficult fight, we can attain what I believe should be among our strategic objectives: above all an Afghan people who do not provide a safe haven for Al Qaeda, reject the rule of the Taliban and support the legitimate government that they have elected and in which they have a stake.
Modest, yet that does seem to imply no limited power-sharing deal with the Taliban, as some have suggested. And talk of a "legitimate" and "elected" government would seem to rule out the imposition of a US-backed strongman. So we're not in total realistville just yet.