I'm not sure on the credibility of OP's image. Apple has been all about making products thin and less bulky, but in reality, there is such thing as "too thin"
I own a 4th Gen iPod touch and it has a case with a rubber gasket surrounding the surface. This exact case, in fact:
http://bit.ly/eqT0XA
I tried using it w/o the case once and I thought I was going to drop it most of the time, mainly because there isn't a lot of room to hold on. With the rubber around the case, it allows for more grip, while adding thickness to the device.
On the subject of the home button, the home button on my iPod touch sometimes does not respond. I think the home button on the new iPhone should be touch sensitive, but keep the design per OP's image.
I know it may seem like I am comparing apples and oranges, but It's the truth. Sometimes you need thickness on a device so you can hold it.