When looking at resources found in the latest version of Apple's iPhone SDK, it looks as though that the handset might be getting in with HDR support since another icon that indicates HDR photos seemingly popped up for non-Retina displays. Additionally, the labeling process with the icon for the Retina display is labeled as “@2x,” while the non-Retina display icon does not have any title associated to it. Just on that, we could all assume at this point that Apple is still showing the love for 3GS owners, but it's far from an official confirmation at this point.
Nevertheless, it does give some hope for those 3GS owners who decided to stick with their last-gen handset as opposed to moving up to the newer hardware.
Apple iPhone 3GS Specifications | Review