Reputedly, Apple has developed flat display glass for a future Watch Series device. According to reports, the intended smartwatch could be the Watch Series 8, which is destined for a September release.
https://www.notebookcheck.net/Apple-Watch-Series-8-to-launch-with-a-flat-display-in-major-design-change.620354.0.html
I mean I wouldn't call it a major redesign change. It's the same square display. It's just flatten now and it wasn't that much curved in the first place.