There will always be conflict, there will always be war.
There will always be people willing to risk their lives for the side they stand with, and people willing to throw legions of said life riskers at their enemies.
There will always be someone who will rise and try to "conquer the world" and someone to confront them.
There will always be two sides who will shoot at eachother over a misunderstanding.
There will always be religious Zealots who believe killing non-believers is the way to attain eternal salvation, and there will always be someone to confront them.
And if humankind ever stops fighting amongst it's self (which I do find highly unlikely) I believe that we will have found other sentient beings to fight against by that point.
In the end the main driving force behind most human actions is them selves. Not always, there are truly benevolent people in this world, but there are not and never will be enough of said truly benevolent people to put an end to war in it's entirety.