The Taliban share power with the Afghan regime, at least for a respectable amount of time.
The new Afghan administration outlaws al Qaeda and closes down any al Qaeda installations within Afghanistan's borders.
Foreign troops leave Afghanistan.
UN observes are allowed to move freely throughout Afghanistan to ensure the deal goes through.
Should al Qaeda return or if the Taliban acts with wanton cruelty against Karsai and his regime, the US will devastate the Taliban again, this time without much thought to "rebuilding" Afghanistan.
The hunt for al Qaeda becomes the problem of the US and the Pakistanis.
It's a simple deal, and it seems to be the one that's taking shape. Strangely, the Saudis are the only power that can broker this deal. After all, they created the intellectual and religious underpinnings of the Taliban in the Wahabbi "schools" the Saudis built in Afghanistan to undermine the Russian occupation and to occupy the attention of zealots like bin Laden.