Major power wars have largely been aided since the end of WWII because world leaders wisely put in place a set of global institutions of cooperation, like the United Nations. Democracies don't tend to attack other democracies, and the spread of international trade has linked countries together in a prosperity of interdependence. That's why major power conflicts have been largely non-existent since (and the major one with the USSR didn't involve two democracies or countries linked by trade).
So... as long as we don't see any major disruptions to global institutions and alliances, democratic norms remain strong, and free trade continues, we shouldn't see any major power wars.