iPod Touch / iPhone (and maybe later a hybrid of the Touch and the iPod Classic, combining a big ol' Classic hard drive with an iOS touch interface)
)
This isn't gonna happen. The hard drive in an iPod touch would be prone to more breakage. With the accelerometer, gyroscope, and constant contact with the screen (not to mention few of games require shaking), the hard drive wouldn't last as long as the current iPod classic.
The iPod touch can't have moving parts.