The next-generation iPad appears likely to have tapered sides and a flat back, very similar to the current iPod touch. This contrasts with the current iPad, which offers flat sides and a slightly curved back.
And there’s a hole in the back about the size of the camera hole found on the back of the iPhone 4. If this rumor is true, I’m not sure why Apple would move away from the flat sides on the current iPad to a tapered design. The iPhone just went from tapered to flat sides and I would think Apple would keep the flat side design for a while. Even the MacBook Pros, iMacs and Cinema Displays have flat sides.