i do not have an old card i am using the video card from the motherboard and its already built comp
Ah, then that changes it of course... You always have the option of getting a $50 video card now and getting a ~$200 better one when that game comes out. The $50 card will probably be better than your motherboard video is, so you'll be able to play all your current games in the mean time. Since the tech always moves and prices do as well, you might actually be better off having spent $250 total ($50 today, $200 later) than if you spend $200 today, depending on how much time away "Diablo 3 and etc" is.
Just consider the different alternatives and do what you think is best.