Bigger 360 Harddrive

I know that Microsoft is going to release a bigger 360 harddrive, but does anyone know yet? Even a guess. My hardrive now is almost full and when I get FF XI it's going to have even less space.

*Note*: I only have game saves on my HD. No music, no videos or demos.

as seen here

http://www.xbox.com/en-US/hardware/x/xbox360harddrive120GB/