I know it's going to sound totally out there, but I think Japan will have an important role in it

.
I know what ya'll think: "Japan?

Is he mad???

", but I think the next war will start in two arenas, the middle-east and the far east.
The far east is getting more and more important, and it's nations more and more determined to play dominant part in global affairs.
India vs. Pakistan\China, China vs. Taiwan, North vs. South Koreas, Malasyia\Indonesia vs. Singapore, Japan vs. the countries they comitted war crimes back in WW2 (China, Korea).
Two much bad blood between all those countries.
In amid all that, there is the fact that 100% of Japan's natural resources are imported, with 88% of it's oil comming from the Middle East (and by that tops every other country, even the US and the EU).
Japan also feels threatened by North Korea, and is hated by most of it's neighbors.
Japan is a super power without a military.
It has one of the strongest economies in the world.
It has a huge population (130 million).
It's living standards are one of the highest in the world.
It is third, after the US and France, in usage of nuclear reactors as power source.
The Japanese Yen is the third most common reserve money around the world (after the US$ and the Euro).
Japan already debates the possibility to alter it's constitution to allow it to have nuclear weapons. In such case, it will become a nuclear power in weeks, not months.
Japan also has huge interest in whatever happans in the Middle-East.
In case it's oild supply will be distrupted, it's reaction might even become military one.
So, IMHO, the next war won't start in Europe or the US, but in the middle east and east asia, with those two campaigns interconnected.