Historically they've been a U.S. ally, as in the Soviet-Afghan war and subsequently after the 9/11 attacks by helping to fight Mid-East terrorism in their country, as well as by publicly ending their support for the Taliban.
However, tensions arose after sanctions were applied by the U.S. in response to Pakistan's nuclear programs, in the mid '90s I think it was.
Considering their issues with India, I don't think they would back down on their front with India to pursue some offensive plans against or with other Mid-East countries. They would probably become stubborn about lowering their military strength with regards to India and so would not be able to or want to raise the resources necessary to create a second 'front'. However, I will say I don't know their strengths in comparison to other Mid-East countries such as Iran or Asian countries such as India so I can't say for sure if they would have the power to commit resources to another conflict.
There is the very unlikely possibility, but a possibility nonetheless, that the regional conflict could possibly be the diversion that Pakistan would need to seize the Kashmir region that they have been longing for. Though I think that doubtful as it would have post-conflict consequences, especially since the two great powers in the region, China and India, will have noticed the seizure.
However, I would have to say that I think they would remain neutral, at least in the early stages, in the conflict.