In the end, only china has remote interests in the natural resources, mostly iron and copper, present in afghanistan. No matter who wins this war, if Afhganistan is to be a viable state economically, it will have to seek businees from china. Also, presently only china has the resources to keep afghanistan aflot through ligitimate means (not aid). Tajikistan and other central asian countries will also see alot of money through transit fees, as they already have safe/all year round transport network which can connect china with afghanistan.
Russia set the ball rolling when it allowed china to enter central asia. Now firmly positioned, china can simply outbid anyone who tries to get access to the oil/gas resources there. Just like it outbid everyone to get hold of the iron mine in afghanistan. Money talks!
If china does show any interest in afghanistan it will have to get the regional players involved:
- It will have to make sure that the Taleban break with al-qaeda.
- Iran will not have any problems with a china guaranteed afghanistan - That afghanistan will not be used as a base against Iran.
- Russia will also be ok, if china promises to control the drug traffic problems
- Central asian states, already dependent on china/russia will not have any issues either. They might even see large benefits.
That leaves Pakistan. There is a very strong US/Saudi influence in Pakistan currently (not just army but the civilian govt also). For china to be able to provide the guarantees (to iran, russia, central asia) Pakistan has to play a big role. That can only happen if both China and the US agree on a solution to afghanistan.