For starters it seems that Kuo is not budging on the rumor that the next-gen iPhone will be using glass very prominently in its design, although he seems to add that an all-glass enclosure is not possible due to limitations. “As all-glass casing is not possible at present given technological bottlenecks, a metal frame surrounding the edge is necessary for reinforced structure design.”
He then suggests that a stainless steel edge is a possible choice of material, but he notes that since it costs more than aluminum, it could be limited to the higher-end models (basically the Plus models). “As stainless steel has a better look than aluminum and costs more, we expect only high-end new iPhone models to come with a stainless steel frame next year.”
We’re not sure if by this he means that the other “regular” models will stick to aluminum. Other rumors we’ve heard so far include the 2017 iPhone being called the iPhone 8, and that it will ditch the home button entirely in favor of a virtual one.