WatchOS 4 was introduced during the last WWDC, and like all other operating systems, it is currently in beta.
It does not, however, go hand in hand with the rest, because although everyone was updated to beta 3 a few days ago, watchOS 4 has done so only now.
The update is now available to developers at the Apple Developer Portal
The update will also appear as available in the Watch application of our iPhone, as long as we have the beta 3 of iOS 11 installed.
To proceed with the installation, we will have to have more than 50% of battery on the clock as well as have it connected to the charger.
Currently, Apple does not offer a public beta of watchOS 4 to those who are subscribed to the public beta program.
This is not a stable version as it can be iOS11, so surely that is why they have not yet released more people. Be that as it may, it looks like we will not see a public watchOS beta 4.
Remember that watchOS 4 brings a few interesting novelties on the Apple watch in addition to the spheres of Toy Story.
The applications have slightly changed its interface, we can navigate in list mode and above all the system focuses more on sport and activity than anything else. In autumn we will see the first official version for all users.