Refreshed internals, lower price point possible.
Comparison of 'iPhone 4S' Antenna Band to GSM and CDMA iPhone 4
The iPhone 4S antenna band is essentially a hybrid of the two earlier designs, showing the same four breaks as the CDMA iPhone 4 but with a SIM-card slot as in the GSM iPhone 4. In the photos, the GSM iPhone 4 antenna band is on top (labeled "4G"), the iPhone 4S antenna band is in the middle (labeled "5G or 4GS"), and the CDMA iPhone 4 is on the bottom (labeled "CDMA").
Interestingly, this is not the first time this particular design for the antenna band has surfaced, as a similar part appeared as long ago as early January, before the CDMA iPhone 4 had even been unveiled. That part was the first to show the shift in the antenna breaks that also necessitated a slight shift in the position of the mute switch on the CDMA iPhone 4, but also contained a SIM-card slot.
A number of parts appearing very similar to their iPhone 4 counterparts have surfaced in recent weeks, with the suggestion being that these could for a low-end "iPhone 4S" model being developed by Apple. The company has also been rumored to be developing a more significantly updated iPhone 5 offering a thinner design, although little has been seen of this design beyond third-party cases based on a claimed leaked design document.