The 20th-anniversary iPhone will get solid-state buttons with haptic feedback on the sides, if claims about the curved-glass model turn out to be correct. Apple is expected to be bringing out the 20th-anniversary edition of the iPhone in 2027, and there have been many wild claims about the model. Now, it is believed that the release will bring with it an often-rumored technology to its edges. In a post to Weibo, serial leaker Instant Digital wrote on Tuesday about the various features they say will be included in the 20th-anniversary iPhone. While most of the features are fairly normal-sounding bits of speculation, it leads off with a hefty discussion about buttons . To Instant Digital, the anniversary model will include a solid-state button on the edge. Apparently, it is a feature that is still undergoing testing in a variety of situations. This includes being used with gloves, wet hands, under extreme temperatures, and through a case.…