Well, IMO, whatever they do, they need to bring back the ambient light sensor!
An app that allowed for changing the backlight to a lower or upper setting automatically would be great too and would save time having to pop into the settings app, although it would probably break Apple's rules somehow... I feel like dropping the camera on the Nano was no NBD, but dropping the light sensor on the Touch was a step too far... Although I love the larger screen.
Apple created the iPod, and they can kill it I guess. There will still be a market for the right one(s).
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Good question. The iPod classic doesn't have the iOS in-your-face, and it works quite well.
If I worked at Apple and had a say in what survives of the iPod line, I'd give the Classic flash memory, and keep the Nano. Maybe give it a clip on the back, and stuff the rest of them. You have two products: One small for sports/etc, and one for music hoarders and travelers that don't want to burn through their iPhone batteries on long flights/drives.
Make the flash based Classic 256G, and the Nano 16G. The Touch is so much like the iPhone, it should BE the iPhone... (But I do like my Touch (with a light sensor))
EDIT: Although a case could be made for a 256G Touch, because it would be multifunction, and killing the Classic...