Xbox 360 console modern warfare 2 edition ( not the game)?

i know there is a xbox 360 modern warefare edition that comes with cod: modern warfare 2 and a 250 hdd.....my question about it is will m.s sell a 250hd by itself and or will the 250hd be added to the black or white systems?.....if so does anyone know when theyll be out ( systems with 250 hd)