1) Up to now, the US has counted on the logistics along route from Basra northward to be relatively safe for a good stretch. That may no longer be the case after this is dealt with at all. And if the British withdraw, then we pull troops form where to cover this? Even if the British do not withdraw, we still will need something more there going forward. And, I really doubt the Iraqi regulars will (or even could be) be entrusted with that need. Can we kiss any draw down goodbye?

2) Basra Mahdi do not owe alligence to Al-Sadr afaik. There is another figure whom they follow instead (name escapes me). This point also seems to escape MSM news posts and most web commentary alike lately. The bottom line here is that there is another player in all this we are not really factoring. What is his current relationship to Al-Sadr? And visa versa? Both would seem an important issue yes?

3) So lets say we crush the open resistance from the Mahdi militias? Now what? Who occupies the formerly relatively quiescent areas that were once controlled by the Mahdi? US? Maliki's troops? Mercenaries? Why does this smell like another another Sunni versus US resistance scenario to me? What happens to those all important oil pipelines if the Basra Mahdi no longer get their cut?

4) So what does Al-Sadr do? A good question. He has? to know direct military action is not going to work in the short run. Does he have reasonable control of his men? Will he work with his ties with Sunni groups? Interestingly enough he has worked with (at least one) Sunni faction actively in the past, so that could bode ill. Will he go underground? Will he take the 'high' road and stay political?
Personally Al-Sadr seems concerned primarily with Al-Sadr, so I bet he keeps up the the latter while disavowing actions his men may tack in clandestine war, but who knows?