World War IV may last longer than World War III (The Cold War) since it is actually a continuation of Islam's war against the West that has run hot and cold for centuries.
I dont think so. A world war is a declared open war between several nations. WWIII has not yet happened, but seems to be the looming Islamic advance into Europe. WWIV will be the West retaking these European losses and a complete clean sweep of the militant regimes rising in the Middle east.