Richard Ned Lebow has an interesting piece in the journal International Relations, arguing major interstate war will become increasingly less likely:

The Past and Future of War
Richard Ned Lebow
Abstract

An original data set of wars from 1648 to the present indicates that security and material interest are rarely the principal motives for war for rising, great or dominant powers. These states far more often go to war for reasons of standing. The empirical evidence offers no support for power transition, balance of power, Marxist or rationalist theories of war. The frequency of war between and among rising, great and dominant powers is likely to decline precipitously because the most important motives for war in the past — standing, security, revenge, material interests and domestic politics — are, for the most part, no longer served effectively by war. Changes in ideas, not changes in material conditions, are primarily responsible for this transformation.
I can't post the whole thing, but folks with online institutional access to the journal can access it here.