The technology behind the eye-tracking isn't known, although Samsung has filed for trademarks to call it "Eye Scroll" in both Europe and the U.S. The GSIII today has Smart Stay, a software feature that uses the front-facing camera to keep the screen lit up when a person is looking at it, instead of dimming after awhile to save power.
Milanesi warned: "Eye-tracking needs to work flawlessly in order not to annoy users. It also might come across as a gimmick versus a real benefit."
Llamas said he didn't think he would use a feature like Eye Scroll, but he predicted the technology would introduce a whole series of facial and hand-gesture tracking innovations from Samsung.
"If Samsung is using the front-facing camera to track your eyes to scroll through an article, that's a pretty neat thing," Llamas said. "The front-facing camera is underused."
He also foresees a time that a user will make a gesture with a hand left to right in front of a smartphone to answer a call, with the reverse gesture indicating the call should go to voice mail.
Regarding the likelihood of a plastic body in the GS4, Milanesi said that as HTC and others "step up their game [with aluminum], Samsung needs to be careful that its devices do not feel cheaper than their price tag. It might be time to look at something other than plastic."
Samsung told CNET recently that bendable plastic makes it easier to open the back cover to remove a battery and to absorb physical impacts. Also, the company considers how quickly and efficiently it can manufacture a product. That factor tends to favor incorporating plastic over aluminum.
While the GS4's screen resolution is expected to be 440 PPI (or higher), according to various reports, Llamas questioned how important that would be, although it seems impressive when compared to the GSIII and the iPhone 5, both at above 300 PPI. (The GSIII has 306 PPI, while the iPhone 5 has 326 PPI.)
"The human eye is only capable of detecting 340 PPI," Llamas said. "Will people notice?"
Much the same can be said for whether the GS4 has a quad-core or an eight-core processor. "Aside from the actual specs, will people even notice?" Llamas said.
A Japanese blog, RBMen, suggested the processor could be clocked at 1.9 GHz, possibly running a quad-core Qualcomm Snapdragon processor. Either processor would probably require boosting the 2100 mAh battery seen in today's GSIII.
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