Not Thinner Nor Lighter
The current iPod touch is only 7.2mm thick! I think that Apple are even having problems updating the iPod touch since it's too thin (which may explain there being no update to 2011's Fall event) so it may have the exact same form factor (even though I would love for them to redesign to become like the iPhone).
Apple probably planned this out, with the next iPhone & iPad to probably have an A6 chip they wanted to keep the iPod touch a bit slower, making the iPod touch have the A5 chip rather than being up-to-date with the upcoming models... This is probably another issue from how thin the product is.
Same Battery Life (or maybe even worse!)
This wouldn't be surprising, but I hope Apple can make the iPod touch's battery life a bit better.
Updating the Screen
The thing is, I don't want to write about them making a 4-inch screen with the iPod because I do have my doubts about Apple making a screen like that, but if they did I'm sure Apple wouldn't leave the iPod touch hanging. But the screen size is not the only thing the iPod touch lacks, it lacks oleophobic screens (which the iPhone had for the past 3 years) and the IPS technology that is found on both the iPad and the iPhone, and keeping the screen the same on the iPod touch would really not do justice for the Retina Display found on the iPod touch.
Better Cameras (But not that great...)
The cameras on the iPod touch are just bad, and I really don't know what Apple were thinking! The Retina Display is not something to take lightly, and adding a crappy camera to the iPod touch just makes everything worse since we can see every little flaw with the camera in great detail! Now, I don't think that they will be updating the camera to 8 megapixels, with 1080p video recording, but I do think that they will be updating the iPod to have a livable camera.
Roughing Up The Edges?
I mean, the iPod touch operates iOS 5 badly, and that's understandable since it has the A4 chip, but I don't think they will keep it that way for long... I still believe that Apple won't make the jump from A4 to A6, but I do think that the iPod will have some kind of in-the-middle thing, so that iOS 6 will run smoothly.