Otterbox is a major case manufacturer, as most smartphone owners probably know, and seemingly wouldn't make a mistake such as putting iPhone 4S on a box when they meant iPhone 4.
The first images showed only the back of the cases and the case boxes. Since then, the Twitter images were posted to img.ly, and clearly show the 4S text on the front side of the case box.
Notably, the photos of the back of Speck and Otterbox cases appear similar to existing case for the iPhone 4, which, as those who recall the non-changed-at-all-on-the-outside iPhone 3GS (as opposed to the earlier iPhone 3G), makes sense. One crucial difference noted was larger cutouts where an iPhone's camera and flash would normally be positioned.
Although this seems to cement the iPhone 4S as "real," the question remains: will there be an iPhone 5 as well as an iPhone 4S, which would be minimally changed externally?
October 4, though still officially unannounced as the launch event of the iPhone 5 / 4S / both, is still looking good as the day of the announcement. Obviously, for iDevice fans, it can't come fast enough.