Meh, I have no use for that much memory on such a device. I have never used the full capacity of my current Shuffle. The reason is that there isn't that much music that I would want to listen to on shuffle-mode anyway. I have a pretty large library, but if I'm listening on shuffle, I want to at least keep it in a certain range of music that would never be so big as to take up 2GB of space. And navigation through that much music without playlists is impossible.
I know it would negate the name of the device, but what would be really great is if they enabled playlists on the Shuffle. You wouldn't need a screen, or even any extra buttons. Just double click the back/forward buttons to move up and down your playlists. I don't know, just an idea I think would really make the Shuffle more usable and put all that memory to better use.