One of the disappointments many people felt when Apple announced the iPhone 4S was the lack of a redesigned chassis. After so many rumors of a new design, many were unhappy that Apple had decided to stick with the iPhone 4 design we’re all familiar with.

We all consoled ourselves with the fact that our existing iPhone 4 accessories and cases would fit the new iPhone 4S, but it seems that might not be the case (if you’ll pardon the pun!) after all…

The key to the issue is in the placement of the hold button, as well as the two volume controls. While the iPhone 4 and 4S handsets may look the same to the untrained eye, they actually aren’t, unless you happen to have a CDMA iPhone 4.

As the image above shows, the iPhone 4S is actually the same as the CDMA iPhone 4, which isn’t quite the same as the GSM release of the world’s best-selling smartphone. Notice the ever-so-slightly different placement of all three controls on the side. What this means is that some cases may not fit the new handset. We suspect that all cases made since the CDMA iPhone 4 was released earlier this year will fit fine, due to being made with wider gaps for the buttons.

Apple itself altered their own iPhone 4 bumpers back in January, thanks to the Verizon iPhone’s new design. This is likely the reason the company says their current bumpers will fit both the iPhone 4 and 4S. Will other cases fit? We’re not so sure.

What this all boils down to is confusion amongst iPhone owners as to which cases will and will not fit their shiny new handsets. Confusion which is usually reserved for those carrying Android phones around!

We’ll find out exactly what the outcome is on Friday, when we all start to receive our new iPhone 4S units, but we foresee more than a few existing iPhone 4 owners finding their (probably free) bumpers just won’t fit.

Let us know in the comments if that happens to you!