MacRumors published a story that Apple has released the first beta of watchOS 7.3 to registered developers.
Apple Seeds First Beta of watchOS 7.3 to Developers
Apple today seeded the first beta of an upcoming watchOS 7.3 update to developers for testing purposes, with the beta coming two days after the launch of watchOS 7.2 with support for Fitness+, cardio fitness notifications, ECG updates, and more. To install the watchOS 7.3 beta, developers need to download the proper configuration profile from the Apple Developer Center. Once the profile is in place, the watchOS 7.3 beta can be downloaded through the dedicated Apple Watch app on the iPhone by going to General > Software Update.
