The next-gen iPhone 15 Pro models may swap its physical volume and power buttons for solid state versions that use haptic feedback, analyst Min-Chi Kuo wrote in a tweet spotted by MacRumors. The design would be similar to the non-physical home button on the iPhone 7, which used a Taptic Engine to simulate a button press with vibrations. It could also resemble Mac trackpads, which don't move but simulate clicks using similar haptic technology.
Making this work would require additional Taptic Engines on top of the one already in current iPhone models. "There will be Taptic Engines located on the internal left and right sides to provide force feedback to make users feel like they are pressing physical buttons," said Kuo in a tweet thread. "Due to this design change, the number of Taptic Engines used in each iPhone will increase from the current one to three."
My latest survey indicates that the volume button and power button of two high-end iPhone 15/2H23 new iPhone models may adopt a solid-state button design (similar to the home button design of iPhone 7/8/SE2 & 3) to replace the physical/mechanical button design.
— 郭明錤 (Ming-Chi Kuo) (@mingchikuo) October 28, 2022
Apple was reportedly planning a similar change for the Watch to increase water resistance, according to a 2018 rumor, but it never happened. It's not clear how a buttonless design would benefit an iPhone, though, as it seems like two additional Taptic Engines would add rather than reduce complexity (a large part of the Watch Ultra's heft is due to the massive Taptic Engine).
Kuo said that the buttonless design and switch to USB-C (which Apple already confirmed) would be two of the major changes for the next iPhone Pro models. Kuo is often right about such things, but the iPhone 15 models are still a year away, so a lot can change in the meantime.