For background and context, readers are directed to: http://www.cnas.org/blogs/abumuqawama/2009/08/maybe-bacevich-has-point-introducing-afghanistan-strategy-dialogue.html.
To begin, the primary question is worded in a misleading fashion. Restated as: In the present war, is the Afghanistan Campaign in the interests of the United States and its allies?, it becomes clear that any such strategy must take into account US and allied intentions throughout that region of the globe and not be artificially limited to Afghanistan-centric concerns only.
It should also be acknowledged that, should it be decided that US and allied war aims are not best furthered by continuance of the Afghanistan Campaign, the US retains the capability to re-stage the 2001/02 intervention should post-withdrawal circumstance require. That said, by creating a regional alliance with India and Iraq, the US could find itself in a position to actively engage the government of Pakistan as well as some future government of Iran in the creation of a regional partnership. Such a structure would provide ample resources to relieve the US of much of the personnel burden as well as provide extensive and varied training/basing options for US and allied assets (not necessarily limited to military assets only) across the region.
The suggested alliance would have the explicit aim of countering instability issues among the member countries as well as to provide permanent staging facilities from which to support current and future war aims throughout that part of the globe, specifically to include military incursions into the African sub-continent. Additionally, creating the necessary logistical infrastructure within the partner countries would explicitly be undertaken to develop and expand related societal infrastructure using indigenous populations and resources to the greatest extent practicable.
Based upon the US experience with the Euro-centric NATO alliance, I anticipate that such an alliance as the one suggested herein ought to provide a 40 to 60 year long engagement effort. The over-riding objective being to create an unreceptive environment for those who seek to oppose US and allied war efforts and objectives, development of regional national capabilities to viable self-reliance levels will offer a gradual reduction in dependance upon US financing and technology contributions as the alliance matures.