iOS 12.1.3 for developers is already available alongside with the beta 2 of tvOS 12.1.2 and watchOS 5.1.3.
Both the Apple Watch and the Apple TV new betas, do not offer major update unless it has been detected at the moment and will focus on solving the operating errors that may occur and correct some bugs. If you are users of the public betas program, you will have to wait a few hours to be able to try tvOS 12.1.2 beta 2.
At the moment, Apple still does not offer a public beta of watchOS, because any user from home cannot restore the device, forcing the community of developers to go to an Apple Store to restore the Apple Watch if you run into some issues while using the betas, something that at the moment has not happened, at least we do not know of any case until the moment.
If you are Mac users, you should know that Apple also released the second beta of macOS 10.14.3 to registered developers, a beta just like previous ones focus on correcting errors and bugs without offering any new features. It seems that the ideas that Apple had planned to implement in iOS 12 are all available now, so everything seems to indicate that we will have to wait until iOS 13, to see what will be the next news with which we will be able to get more out of it both our iPhone and our iPad, in addition to Apple Watch and Apple TV.