From most-wanted to least-wanted:
A5. Even if it needs to be clocked down a little bit, I couldn't imagine the iPod Touch selling nearly as well if it lagged greatly behind the iPhone and iPad performance-wise. This could work to their advantage and drive people to the iPad, or it could just drive people to find something else. Personally, I prefer the Touch to the iPad due to the form factor, yet still being able to do everything I'd like.
16GB base model. 8GB is okay if all you do is app-related, but I'm finding myself using the iPod for a lot more than I expected. (Admittedly, partly due to jailbreaking it. Gotta love MxTube.) I cycle my media so it's not too big a bother, but it'd still be nice.
Mute switch/button. Good lord, I hate having to dig through menus to mute the thing entirely! Nothing like getting a notification somewhere you'd like it to be completely silent and realizing you forgot to mute the alerts. Alternately, it could be a configurable switch like the iPad 2 has...
3G model. Okay, I personally wouldn't use one, but for those who don't want a full-on phone (or have another), but still wish for internet access on the go. Of course, we'd want a wifi-only model as well, just like the iPad.
512MB of RAM. This is low on the list since, well... I haven't encountered any performance issues with the iPod's 256MB.
Camera improvement. I, personally, find the iPod Touch camera as it is now, rather decent. Low-res, but since I usually shrink my photos to 512x384 before sharing... (okay, old practice from the 56k days... but eh.) Perhaps even a camera like the 3G/3GS would work - some people seem to quite like the 3GS's camera, from what I can tell!
Granted, only the lack of a button/switch and the 8GB capacity instead of 16 are the only things that truly bother me... most of these are evolutionary changes I'd really hope the line gets to keep it selling well and competitive. Not surprised all of the concerns I had were addressed before, actually...