I don't think there could be a war today that would be big enough to cause World War 3, but I won't count it out. I think worse case scenario, there's a war between China, Russia, U.S.A., Iran, and North Korea. Best case scenario, the Korean War simply flares up again, in the scenario that war is imminent.
"There is no such thing as coincidence, only inevitability" - xxxHoLiC
"Justice? But I don't serve justice, Watson, I serve the truth." - Sherlock Holmes