A senior US Army commander today told the CNN that there is no indication that Nasiruddin Haqqani was indeed detained. Now, generally, the ordinary US soldier would not know this type of information, but this officer was the US operations commander of the region where the Haqqani Network operates, so he is bound to know (the region around Khost, I believe).
See, the Haqqani Network on its own is neither powerful enough nor influential enough in greater Afghanistan to pose any serious threat to the post-ISAF government of Afghanistan. This is why, as far as I am aware, even Hamid Karzai is in favor of favorable dealings with them. That puts the two main parties, Pakistan and Afghanistan, on the same page vis-a-vis the Haqqani Network (i.e. reconciliation). The only problem are the NATO forces who do not want to make any deals with the Haqqani Network. This seems to be now a matter of saving face rather than peace in Afghanistan.
Pakistan, mainly the ISI, sees the Haqqani Network as a hedge against India's growing influence in Afghanistan. I believe that once the NATO forces have departed, the ISI will use the HN to wreak havoc in the Indian presence in Kandahar, Jalalabad and stop them from funding, arming and even training the Baloch insurgency. Without the HN, Pakistan will have to resort to dealing with the Taliban directly, or even Al-Qaeda. Also, Pakistan also sees the HN as a path to reconciliation with the Taliban post-ISAF, which is again important if Pakistan wants to be influential in Afghanistan.
Afghanistan's government, on the other hand, sees the HN as a possible post-ISAF ally that could help keep the government intact by keeping the Taliban at bay. Like I said, the HN neither has the means, nor the desire to take over Afghanistan, as long as their sphere of influence remains firmly under their control.
So, the question that remains is, what will it take for the NATO forces to stop its campaign against the HN and facilitate an alliance? Also, what would India do to ensure such an alliance never takes place?
I think that the Nasiruddin Haqqani detainment was merely for show, or a part of a bigger plan. I highly doubt the ISI would want to jeopardize its relations with the HN for minor gains in the short term.