@ Spike it is not so simple, you are talking about WOW which is a MMORPG, where player is in an great universe with other real persons, that doesn't need high end specs because the graphics not focused to be realistic.

In a First Person Shooter in singleplayer the player is alone and there is really a need of realism and atmosphere. So please don't start a comparison between such different game types. More realism needs more power that was it what happened in the past and will happen in the future, by the time our game comes out there will be much more power at home computers, than you need to run the game at high quality.