Islamabad wont fall into Taliban hands however i could still see military intervention but i hope not.
You have a lot of faith in the Pakistani military, more so than I do (which is none at all).
you have too much faith in the Taliban, they aren't cable of defeating the Pakistani military on ground that is not favorable to them, the Pakistani military isn't competent but that does not make them incapable of defending the capital of Pakistan from a bunch of ragtag warriors look at Peshawar for instance yes its becoming a haven for Taliban and they have alot of influence in the city, but the Taliban still don't control the city militarily and that city lies right on the edge of Taliban controlled area.