With the dollar cost of the Iraq war showing just how expensive it is to wage large-scale warfare, I think proxy wars will be the wave of the future. Equip the Darfur rebels to harass the Chinese-supported Sudanese government and oil establishment. Send a never-ending stream of militants into Iraq to keep the US involved indefinitely. Support/intimidate Georgia/Taiwan/Israel. A little push in any one of these places can cause problems that the large nations of the world can't afford to ignore.
However, when the next big war occurs, it's going to be in Central or East Asia. Too many people, too much growth, too many religions, too many cultures. I'm in this contest, I'm dating a virgin, something's gotta give!