Apple first released developer betas of iOS 10.2.1, macOS 10.12.3 Sierra, and tvOS 10.1.1 on December 14, with watchOS 3.1.3 following a week later. It's taken quite a while to release such minor updates, but as of today, they're now available to the public.
In fact, as their version numbers indicate, they don't even qualify as minor updates, and there aren't any new front-facing features. Instead, each of these updates focuses on bug fixes and stability improvements.
There are a couple of things that are noteworthy though. watchOS 3.1.3 actually skips right over 3.1.2, which was never offered to developers or the public. Presumably, this has something to do with Apple pulling the 3.1.1 update after it started bricking devices.
There were also rumors earlier this month that there would be an iOS 10.3 Developer Beta arriving on January 10. Obviously, it never arrived, which isn't entirely surprising given that 10.2.1 was still in beta, but it was rumored to have a new Theatre Mode, which kept the Internet guessing for a time as to what that might be.
iOS 10.2.1, macOS 10.12.3 Sierra, watchOS 3.1.3, and tvOS 10.1.1 are all available now, and you can update your respective devices through Settings.