Following iOS 10 and macOS Sierra releases, Apple on Tuesday issued beta 5 of both tvOS 10 and watchOS 3. Registered developers with updated profiles can install the over-the-air updates via the Watch app in iOS 10, or the Update mechanism in tvOS 10.
The updates come just a week after Apple sent out fourth betas to developers, suggesting we are now in the finishing touches stage ahead of their expected fall releases. Both tvOS 10 and watchOS 3 have been in beta since they were introduced in June.