First question you need to answer is, why are terrorists targeting only cricketing events? Why weren't there any such concerns about the ECO summit in Islamabad? Wouldn't a small blast in Islamabad or Rawalpindi have equally adverse effects?
I am sure that even if one or two International players come (Sammy and Samuels have already agreed to come) and the event passes without an incident, next year we will see more foreign players willing to come to Pakistan and then the next step would be to invite an International team. This is a risk that we "MUST" take.
This is how Euro 2016 was played in France.
Even if we get rid of all sorts of terrorism in Pakistan and play a cricket match after 10 years, the level of security will be the same as it would be today.