I think as the world becomes more connected (in terms of trade, culture, the internet, etc), the probability of a world-war increases. Violence/war itself seem to be an inherent characteristic of our species. Although the per-capita amount of violent acts in the world may be decreasing, there are still large systematic shifts in power that can happen as a result of our highly structured and connected networks of economy, culture, and information. In other words (and I sincerely hope I am wrong), the probability of another world-war is only increasing. However, this highly connectedness exposes a world dichotomy in general philosophy of leadership, religion, and politics. Hopefully the spread of information through the internet will allow this dichotomy to become less of a problem. Answering the question of predictability is much more difficult.