World War III already ended... the next one would be WW IV.
WW III is the correct term to define the US vs USSR by-proxy wars. Actually they caused more havoc and victims than WW 2...
I think people only consider a World War when people actually engage each other.
America have "boot on the ground" in Iraq, Afghanistan, Pakistan, Somalia, Yemen, and now Libya.
How many countries does America need to invade before people call it a World War?
If fight wars on more than one continent is what qualifies as a World War, I'd say we're there already.