watchOS 26 Support Floor Cuts Off Series 4 and 5 Users

Apple's watchOS 26, released September 2025, requires Apple Watch Series 6 hardware or later, locking Series 4 and Series 5 owners out of the new software. The Series 6 floor—nearly five years old—likely reflects sensor capability thresholds rather than arbitrary deprecation, but affects a non-trivial installed base accustomed to longer wrist hardware retention cycles.