I think WWIII will come when we least expect it. I was thinking about the whole Korea scenario, but it has been going on for a while now, and nothing. Then again, WWII didn't just happen overnight.
World War 3 will not occur with the current state of nuclear weapons in many of the worlds super powers. If a country attacks, any allies of the country attacked will retaliate with nukes. It's too much damage for such a minuscule reason.
It's not going to happen. If it did the only weapons we would fight with would be chemical and by saying that, half the worlds population would be deceased. Then nearlly 50% of the living after that would be affected by nuclear war meaning their life span is shortened by 20-30 years.
It just wont happen, there is too much at stake. What we really need to think about is leaving earth and try and find another planet to harvest and destroy.
World War 3 will never happen. The negotiation policies put in place between countries in conflict simply would knock out the threat of any major World war.