Not going to happen. I think as long as there are conflicts in the world, and the long ass history of conflicts we'll continue to see plenty-a-FPS games coming out for the next few decades. The genre is just too extensive and fuelled by the desire to fire a gun and to be the "Hero" as is the case in most FPS games. You'll end up killing a shitload of bad guys, you get the chick, you fornicate, your son is born, he goes off to fight more enemies, he gets a hot chick, they fornicate, then his son goes off etc etc.
So far famous conflicts that FPS genres have touched upon -
Vietnam(Not as much as the others though), Modern, WW1(Not so much), WW2 and maybe a few odd gulf wars. Overall I'd say there is much live left in there, including WW1 and Vietnam. WW2 has been done to shit though >:
Disconnect and self destruct, one bullet a time.
