Very few companies, if any, have domain expertise at the cutting edge of those 3 different devices, so usually when you see combination MP3/Digicam/Cellphone/Toaster devices, one of the functions is lagging. With that in mind, I'm okay with my cell phone, music player, and digital camera all being different devices.

What you're talking about may happen down the line, but I'm talking about something that could be developed now-ish. I admittedly don't know the state of iPod/Karma type HD technology these days, but assuming storage density is going at a nice rate, it can't be that tough of a nut to crack.