The past decade was one of the least violent in modern history. The number and level of civil wars in the world has continued it's steady decline, while interstate war has remained at its steady, low levels. That that is true despite the US wars in Afghanistan and Iraq makes it even more startling.
That war has been declining does not mean that it will continue to do so. The twenty year decline in internal war and a corresponding rise in human security, came during a period when the US was astonishingly dominant in international security, and when the western middle powers had political and financial surpluses to devote to such caused as peacekeeping, humanitarian action, and international justice - including the ICC. All of this now in question, just as the new Middle East and Gulf poses risks of an upswing of internal and regional and international war.
Has the ICC, now a decade old, been a part of the positive trend of the last decade? Probably not much, yet. ICC is to young yet to show real impact. It's had a troubling birth. But the process of international justice has shown it's merit in the Balkans and West Africa, through other international courts.
International institutions take years to develop (as do domestic ones.) The ICC has had a trying first decade. Now, the ICC's challenge will be that it will now come into maturity just as the project of which it was the culminating expression - the project of protecting civilians from the scourge of war - will enter a far more challenging phase. The test for the next decade is: does the existence of a mature ICC help to prevent some of the worst risks that may now unfold, especially in the Arab world. Syria is an early test, but no easy one.