Here are my thoughts.
1. The touch will see a whole new design. We had the same look for the past two years. Seeing a new design that may mock the iPhone would be idea as the frame will be the structure, like unibody. We willow no longer see the mirror backing.
2. The touch will get iOS 4.0 of course.
3. The touch will get a camera. Photo apps will sale even more with the expansion of devices.
4. Facetime will come to the touch. Steve said they will sale tens of millions of face time devices. The touch will be one of them.
5. Volume control buttons may change to the iphone styling
6. Retna display. Same pixels and resolution as the iPhone 4.
7. Orention lock
8. Possisble iPad backing?
9. 32Gb and 64GB storage. $199 and $299 respectfully
10. Possisble 3G version but highly unlikely.
This would all be fantastic. Unfortunately, I think this is not realistic for 4th gen, especially not at $199 and $299. Apple wouldn't be able to sustain its profit margins. Form will probably change to resemble the iPhone 4 but be slightly different in some way. It will be a cheaper build case than iPhone 4, and I don't expect any fancy external rim antenna, since wifi reception isn't as big an issue as 3G/cell phone reception.
As far as cameras, I'm resigned to settle for 3.2MP rear camera and that's it. Or it might be a front camera for Facetime instead. I would be pleasantly shocked if they have both (and would probably buy two - for me and spouse).