I have been a very vocal critic of the shiny chrome backing used on the iPod Touch. I also take all these case leaks with a grain of salt, because I remember all the leaked cases from last year that showed a hole for a camera, and we all remember how that worked out 
However, I'm going to go out on a limb, and assume that the cases leaked for the upcoming Touch are accurate, most notably in the fact that they have a hole on the upper left hand side of the device for a camera. If this is indeed where the camera is placed, then I am thrilled. Why? Because that is where the Touch currently has that ugly piece of black plastic for the Wi-Fi signal to get through, because it cannot get through the rest of that scratch-prone chrome back. So if there's no ugly black plastic oval, then it is reasonable to conclude that the back of the iPod will be made of something other than chrome, because no plastic circle means that the back of the iPod will need to be made of something that a Wi-Fi signal can pass through.
Now I know some people will say oh, Apple will just put the oval on the other side. I doubt it. Apple is always about clean design - just imagine the back of an iPod, with a camera on one side and a black plastic oval on the other. That's not the kind of clean design we've come to know from Apple. Now I could be wrong about that, because the fact that Apple has stuck with the chrome back/ugly black plastic circle for three generations is unimaginable for them. But I don't think that they'll keep it.
So in conclusion, if these leaked cases are right, and Apple really does put a camera on the upper left side of the device, I think you can say goodbye to the chrome backing. I don't think we'll see an iPhone 4 design, but I think we'll finally see the end of chrome. Of course, this could all just be wishful thinking.
However, I'm going to go out on a limb, and assume that the cases leaked for the upcoming Touch are accurate, most notably in the fact that they have a hole on the upper left hand side of the device for a camera. If this is indeed where the camera is placed, then I am thrilled. Why? Because that is where the Touch currently has that ugly piece of black plastic for the Wi-Fi signal to get through, because it cannot get through the rest of that scratch-prone chrome back. So if there's no ugly black plastic oval, then it is reasonable to conclude that the back of the iPod will be made of something other than chrome, because no plastic circle means that the back of the iPod will need to be made of something that a Wi-Fi signal can pass through.
Now I know some people will say oh, Apple will just put the oval on the other side. I doubt it. Apple is always about clean design - just imagine the back of an iPod, with a camera on one side and a black plastic oval on the other. That's not the kind of clean design we've come to know from Apple. Now I could be wrong about that, because the fact that Apple has stuck with the chrome back/ugly black plastic circle for three generations is unimaginable for them. But I don't think that they'll keep it.
So in conclusion, if these leaked cases are right, and Apple really does put a camera on the upper left side of the device, I think you can say goodbye to the chrome backing. I don't think we'll see an iPhone 4 design, but I think we'll finally see the end of chrome. Of course, this could all just be wishful thinking.