This is going to fall through and fizzle out, just like last time (when we heard Pakistan was interested in Chinese SSKs).
Until one or both of the following happen, don't expect any major purchases from Pakistan:
1. Thorough review of US-Pakistan ties in the sense Pakistan will act on its own interests, even if those interests are counter to US interests (e.g. focusing on countering India, meddling in Afghanistan, etc).
2. An end to the fighting in Waziristan, militarily or otherwise. The US does not want to see Pakistan wrap up its internal security problems, it wants to see Pakistan drag its feet and burn its resources, its stability and its focus on the tribal region.