Mark Gurman spent Sunday’s Power On newsletter on what the Apple Watch Series 12 and Ultra 4 will be when Apple shows them on September 9, and the case is not part of it. MacRumors, quoting the newsletter, has him not expecting any major design change from the current Series 11 and Ultra 3. Gurman does report a sensor change: "One new feature in testing allows the heart-rate sensor on the Apple Watch to continuously collect data throughout the day, he said." The sensor fires during workouts and at semi-random intervals today, so collecting all day turns a workout log into a full day of readings. The visible change is smaller, a ceramic case tested in white and dark gray, called iceman inside Apple.
Apple’s Health app rebuild, Project Mulberry, missed iOS 26.4 and then iOS 27, and the newsletter has a revamped Health and Fitness app showing more wellness metrics "in a similar fashion to increasingly popular app offerings from Whoop and Oura" without attaching a date to it. The case for September is Apple’s own habit: it held Low Power Mode in watchOS 9, sleep apnea detection in watchOS 11 and hypertension notifications in watchOS 26 until September, and none of them needed new hardware. The full redesign is further out, aimed at next year and possibly 2028.