The next great war will likely be a long drawn out low intensity conflict (think proxy war with a lot of direct cyber war on the side) that manages to stay under the threshold for opening a can of nuclear whoop-ass. Big powers aren't gonna get in an over the table shooting war if they can avoid it for fear of the other opening that can. I dunno if that kind of situation meets your definition of "great" though.

Edit: The comment I'm replying to changed substantially since I replied.